Optical glass and optical elements

Abstract

To provide an optical glass that can contribute to compensating for the influence of temperature changes on image-forming properties, and also has high weather resistance, suppressing the degradation or fogging of a glass surface even in a severe environment, and an optical element including the same.SOLUTION: An optical glass has a temperature coefficient (40-60°C) of a relative refractive index (589.29 nm) being 0×10-6 (°C-1) or more. Expressed in mol%, Al2O3 / P2O5 is 0.20 or more, and a total content of RO component (in the formula, R is at least one of MgO, CaO, SrO and BaO) is 5.0% or less, and the content of P2O5 component is the highest of the glass composition components.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical glass and an optical element. [Background technology]

[0002] Optical elements incorporated in on-board optical devices such as on-board cameras, and optical elements incorporated in optical devices that generate a lot of heat, such as projectors, copy machines, laser printers, and broadcasting equipment, are increasingly being used in higher temperature environments. In such high-temperature environments, the temperature of optical elements constituting the optical system is likely to fluctuate significantly during use, often reaching temperatures of 100°C or higher. In such cases, the adverse effects of temperature fluctuations on the imaging characteristics of the optical system become significant enough to be unnegligible. Therefore, there is a demand for optical systems whose imaging characteristics are less susceptible to temperature fluctuations.

[0003] In constructing an optical system that is less susceptible to the effects of temperature fluctuations on imaging performance, etc., it is preferable to use both optical elements made of glass whose refractive index decreases as the temperature rises and whose temperature coefficient of the relative refractive index is negative, and optical elements made of glass whose refractive index increases as the temperature rises and whose temperature coefficient of the relative refractive index is positive, in order to be able to correct the effects of temperature changes on imaging performance, etc.

[0004] Glass containing a large amount of the P2O5 component has characteristics in the optical region, but this component also reduces the temperature coefficient of the relative refractive index (Patent Documents 1 and 2). However, the applicant has discovered that the addition of the Al2O3 component can increase the temperature coefficient of the relative refractive index (Patent Document 3).

[0005] On the other hand, because optical glass is used under a variety of conditions, glass with good chemical durability is required. Chemical durability includes weather resistance, acid resistance, water resistance, etc. While acid resistance and water resistance are measured using a powder method, weather resistance is measured using a surface method, and is an indicator that can indicate superior chemical durability of the glass surface than acid resistance or water resistance. Furthermore, while acid resistance and water resistance are indicators of chemical durability that measure chemical durability over a short period of time, weather resistance is an indicator that can measure chemical durability over a longer period of time and in a more severe environment. Patent Document 4 describes glass containing P2O5 and Al2O3 components that has excellent acid resistance.

[0006] When the glass surface deteriorates due to harsh environments, it can develop white spots of cloudiness on the glass surface (white tarnish), or a blue-purple interference color (blue tarnish), and the glass surface can also become sticky or prone to peeling. For example, in "JOGIS07:2019 (Non-Patent Document 1)," the degree of weather resistance is measured by measuring the change in haze on the glass surface before and after the test. However, even if the change in haze is about the same, it does not necessarily mean that the glass surface condition is about the same. In addition, optical elements such as lenses are usually coated with a thin film to prevent scratches on the glass surface, but glass containing a large amount of P2O5 has a high water absorption rate due to the P2O5 component, which makes the coating easily peel off. Furthermore, glass whose surface is easily peeled off is affected by storage conditions such as temperature and humidity during storage and transportation, making it difficult to use as an optical element. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-132510 [Patent Document 2] Japanese Patent Application Publication No. 2019-182680 [Patent Document 3] Patent Application No. 2020-170956 [Patent Document 4] WO2020 / 262014 publication [Non-patent literature]

[0008] [Non-patent document 5] JOGIS07:2019 Measuring method for weather resistance of optical glass Summary of the Invention [Problem to be solved by the invention]

[0009] The glasses described in the examples of Patent Documents 1 and 2 relate to phosphate-based glasses that focus on the temperature coefficient of the relative refractive index, and although they describe glasses with a negative temperature coefficient of the relative refractive index, they do not describe glasses with a temperature coefficient of the relative refractive index of 0 or more. The glass described in Patent Document 3 has been found to increase the relative refractive index of glass containing the P2O5 component and the Al2O3 component, but no consideration has been given to weather resistance. The glass described in Patent Document 4 is an invention that improves acid resistance, which is one of the chemical durability features, but no sufficient consideration has been given to weather resistance.

[0010] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide an optical glass having a temperature coefficient of relative refractive index of 0 or greater, thereby contributing to correction of the effects of temperature changes on imaging characteristics, and which is highly weather-resistant and therefore suppresses deterioration and clouding of the glass surface even in harsh environments, as well as an optical element using the same. [Means for solving the problem]

[0011] In order to solve the above problems, the inventors have conducted extensive testing and research, and as a result, have found that the temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0×10 -6 (℃ -1) or more, in which, in mol %, Al2O3 / P2O5 is 0.20 or more, the total content of RO components (where R is one or more of MgO, CaO, SrO, and BaO) is 5.0% or less, and the optical glass has the highest content of P2O5 component among all the glass composition components, and this has led to the completion of the present invention. Specifically, the present invention provides the following:

[0012] (1) The temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0 × 10 -6 (℃ -1 ) or more glass, In mole %, Al2O3 / P2O5 is 0.20 or more, The total content of RO components (where R is one or more of MgO, CaO, SrO, or BaO) is 5.0% or less and This optical glass has the highest content of P2O5 among all glass components.

[0013] (2) The optical glass according to (1), wherein the molar ratio (P2O5+RO+Li2O) / (P2O5-Al2O3) is 1.30 or more and 1.70 or less.

[0014] (3) Refractive index (n d ) is 1.45000~1.60000, Abbe number (ν d ) is 60.00 to 80.00.

[0015] (4) An optical element made of the optical glass according to any one of (1) to (3). [Effects of the Invention]

[0016] The present invention can provide an optical glass that can contribute to correcting the effects of temperature changes on imaging characteristics and that is highly weather resistant, thereby suppressing deterioration and clouding of the glass surface even in harsh environments, as well as an optical element that uses the same. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the object of the present invention. Note that redundant explanations may be omitted where appropriate, but this does not limit the spirit of the invention.

[0018] [Glass components] The composition ranges of each component constituting the optical glass of the present invention are described below. Throughout this specification, unless otherwise specified, the content of each component is expressed as mole percent relative to the total amount of glass material, calculated as an oxide. Here, "oxide-based composition" is expressed as mole percent relative to the total number of moles, 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 to oxides during melting.

[0019] <About the ingredients> The P2O5 component is a glass-forming oxide component and is the component with the highest content among the components in the glass composition of the present invention. In particular, the stability of the glass can be improved by including 45.0% or more of the P2O5 component. Therefore, the lower limit of the P2O5 content is preferably 45.0% or more, more preferably 47.0% or more, even more preferably 50.0% or more, still more preferably 52.0% or more, even more preferably 53.0% or more, and even more preferably 54.0% or more. On the other hand, by keeping the content of the P2O5 component at 75.0% or less, devitrification of the glass can be reduced and deterioration of weather resistance can be suppressed. Therefore, the upper limit of the content of the P2O5 component is preferably set to 75.0% or less, more preferably 70.0% or less, even more preferably 65.0% or less, and even more preferably 64.0% or less.

[0020] The Al2O3 component is a component that improves the temperature coefficient of the relative refractive index and weather resistance, and therefore the lower limit of the Al2O3 content is preferably 5.0% or more, more preferably 8.0% or more, even more preferably 10.0% or more, still more preferably 13.0% or more, and even more preferably 15.0% or more. On the other hand, by keeping the Al2O3 content at 30.0% or less, deterioration in devitrification resistance due to excessive content can be suppressed. Therefore, the upper limit of the Al2O3 content is preferably 30.0% or less, more preferably 27.0% or less, even more preferably 25.0% or less, still more preferably 23.0% or less, and even more preferably 20.0% or less.

[0021] The Li2O component, Na2O component, and K2O component are components that improve low-temperature melting properties, but excessive inclusion of these components can cause devitrification of the glass and deterioration of weather resistance. In particular, the effect of deteriorating weather resistance is greatest for the Li2O component, followed by the Na2O component and the K2O component.

[0022] The lower limit of the Li2O component is preferably more than 0%, more preferably 0.1% or more, even more preferably 0.3% or more, even more preferably 0.5% or more, and even more preferably 0.8% or more, but the content may be 0%. On the other hand, the upper limit of the content of the Li2O component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, and even more preferably 2.0% or less.

[0023] The lower limit of the content of the NaO component is preferably more than 0%, more preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and even more preferably 1.0% or more, but the content may be 0%. On the other hand, the upper limit of the content of the Na2O component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, and even more preferably 3.0% or less.

[0024] The lower limit of the content of the K2O component is preferably more than 0%, more preferably 1.0% or more, even more preferably 2.0% or more, even more preferably 3.0% or more, and even more preferably 4.0% or more, but the content may be 0%. On the other hand, the upper limit of the content of the K2O component is preferably 25.0% or less, more preferably 22.0% or less, even more preferably 20.0% or less, and even more preferably 18.0% or less.

[0025] The MgO component, CaO component, SrO component, and BaO component are components that improve the low-temperature melting property and increase the temperature coefficient of the relative refractive index, but they are components that deteriorate the weather resistance. In particular, the effect of deteriorating weather resistance is greatest in the order of BaO, SrO, CaO and MgO.

[0026] The lower limit of the content of the MgO component is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, but the content may be 0%. On the other hand, the upper limit of the content of the MgO component is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, and even more preferably 0.5% or less.

[0027] The lower limit of the CaO content is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, but the content may be 0%. On the other hand, the upper limit of the CaO content is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, and even more preferably 0.5% or less.

[0028] The lower limit of the SrO content is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, but the content may be 0%. On the other hand, the upper limit of the content of the SrO component is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, and even more preferably 0.5% or less.

[0029] The lower limit of the BaO content is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more, but the content may be 0%. On the other hand, the upper limit of the content of the BaO component is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, and even more preferably 0.5% or less.

[0030] The ZnO component is a component that can increase the temperature coefficient of the relative refractive index while decreasing the Abbe number. The lower limit of the ZnO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, and even more preferably 2.0% or more, but the content may be 0%. On the other hand, by keeping the ZnO content at 15.0% or less, deterioration in devitrification resistance due to excessive content can be suppressed. Therefore, the upper limit of the ZnO content is preferably 15.0% or less, more preferably 14.5% or less, even more preferably 14.0% or less, still more preferably 13.5% or less, even more preferably 13.0% or less, still more preferably 12.0% or less, and still more preferably 10.0% or less.

[0031] The ZrO2 component is a component that can improve the weather resistance and the refractive index and dispersion of the glass. The lower limit of the content of the ZrO2 component is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more. On the other hand, by limiting the content of the ZrO2 component to 10.0% or less, the stability of the glass can be improved. Therefore, the upper limit of the content of the ZrO2 component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, and still more preferably 4.0% or less.

[0032] The B2O3 component is a component that promotes stable glass formation. On the other hand, excessive B2O3 content can cause devitrification of the glass, so the upper limit of the B2O3 content is preferably 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, even more preferably 2.5% or less, and even more preferably 1.0% or less, but the content may be 0%.

[0033] The SiO2 component is a glass-forming oxide component that can improve the viscosity of the molten glass. On the other hand, excessive inclusion of the SiO2 component leads to devitrification of the glass. In particular, in the present invention, the SiO2 component is characterized by being more likely to cause devitrification than the B2O3 component. Therefore, the upper limit of the SiO2 component content is preferably 10.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably 1.0% or less, but the content may be 0%.

[0034] The La2O3 component, the Gd2O3 component, the Y2O3 component, and the Yb2O3 component are components that can provide a high refractive index. In particular, by keeping the content of each of the La2O3 component, the Gd2O3 component, and the Y2O3 component at 15.0% or less, it is possible to prevent a decrease in the Abbe number, reduce devitrification, and reduce coloration. Therefore, the upper limit of each of the contents of the La2O3 component, the Gd2O3 component, and the Y2O3 component is preferably 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and even more preferably 5.0% or less, but the content may be 0%. On the other hand, the upper limit of the content of the Yb2O3 component is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.5% or less, even more preferably 0.3% or less, even more preferably 0.2% or less, and even more preferably 0.1% or less, but the content may be 0%.

[0035] The TiO2 component is a component that can increase the refractive index of glass. If the content of the TiO2 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the TiO2 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably less than 1.0%, but the content may be 0%.

[0036] The WO3 component is a component that can increase the refractive index of glass. If the content of the WO3 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the WO3 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably less than 1.0%, but the content may be 0%.

[0037] The Nb2O5 component is a component that can increase the refractive index and dispersion of glass. If the content of the Nb2O5 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number, so the upper limit of the content of the Nb2O5 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and still more preferably less than 1.0%, but the content may be 0%.

[0038] The Bi2O3 component is a component that can increase the refractive index and lower the glass transition point. If the content of the Bi2O3 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the Bi2O3 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably less than 1.0%, but the content may be 0%.

[0039] The Ta2O5 component is a component that can increase the refractive index of the glass. If the content of the Ta2O5 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the Ta2O5 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably less than 1.0%. From the viewpoint of reducing material costs, the Ta2O5 component may not be contained.

[0040] The TeO2 component is a component that can increase the refractive index of the glass. If the content of the TeO2 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the TeO2 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably less than 1.0%. From the viewpoint of reducing material costs, the TeO2 component may not be contained.

[0041] The upper limit of the CeO2 content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably none is contained.

[0042] The upper limit of the SnO2 content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and even more preferably none is contained.

[0043] The upper limit of each of the EuO component, Pr2O3 component, Tb2O3 component, and Dy2O3 component is preferably 1.0% or less, more preferably 0.5% or less, even more preferably 0.1% or less, and even more preferably none is contained.

[0044] The F component is a component that provides a defoaming effect while reducing dispersion. In particular, the glass of the present invention contains large amounts of the P2O5 component and the Al2O3 component, which makes bubbles more likely to remain during melting. Therefore, the lower limit of the F component content is preferably more than 0%, more preferably 0.1% or more, even more preferably 0.2% or more, even more preferably 0.5% or more, and even more preferably 1.0% or more, but the content may be 0%. On the other hand, by keeping the content of the F component at 10.0% or less, it is possible to suppress a decrease in the temperature coefficient of the relative refractive index due to the F component. Therefore, the upper limit of the content of the F component is preferably 10.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably 1.5% or less.

[0045] The Sb2O3 component is a component that can defoam glass melt. In particular, the inclusion of Sb2O3 in the glass of the present invention not only provides a defoaming effect, but also reduces knots, which are platinum crystals eroded from the crucible. Similar to bubbles, knots deteriorate the internal quality of the glass, and are therefore problematic when the glass is used in optical elements for automotive applications and projectors. On the other hand, by keeping the content of Sb2O3 at 1.0% or less, it is possible to suppress a decrease in transmittance in the short wavelength region of the visible light spectrum, solarization of the glass, and a deterioration in internal quality. Therefore, the content of Sb2O3 may be preferably set to 1.0% or less, more preferably less than 0.7%, and even more preferably 0.4% or less.

[0046] The sulfur (hereinafter referred to as S) component is a component that can degas the glass melt when its content exceeds 0 ppm. The S component is preferably incorporated by adding, for example, a sulfate component as a glass raw material. The sulfate component is, for example, one selected from lithium sulfate hydrate (LiSO·H0), sodium sulfate (NaSO), potassium sulfate (KSO), magnesium sulfate (MgSO), calcium sulfate hydrate (CaSO·1 / 2H0), strontium sulfate (SrSO), zinc sulfate hydrate (ZnSO·7H0), and lanthanum sulfate hydrate (La(SO)·9H0). The lower limit of the content of the S component is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more. On the other hand, by keeping the S content at 300 ppm or less, alloying and coloring that occur when excessive S is contained can be prevented. Therefore, the upper limit of the S content is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

[0047] The chlorine component is a component capable of degassing the glass melt. The chlorine component is not particularly limited, but can be contained, for example, in a chloride raw material or a chloride gas. The upper limit of the chlorine content, expressed as an exclusive percentage, is preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less, even more preferably 0.4% or less, and most preferably 0.3% or less. On the other hand, the lower limit of the chlorine content, expressed as an exclusive percentage, is preferably 0.01% or more, more preferably 0.03% or more, more preferably 0.05% or more, more preferably 0.08% or more, and even more preferably 0.1% or more.

[0048] Although the Sb2O3 component and the S component each provide a defoaming effect when contained alone, they may also be contained together. In particular, in the glass of the present invention, the inclusion of the Sb2O3 component and / or the S component not only provides a defoaming effect, but also reduces knots, which are platinum crystals eroded from the crucible. Similar to bubbles, knots deteriorate the internal quality of the glass, and are therefore problematic when used in optical elements for automotive applications or projectors. When Sb2O3 and S are contained together, the content of Sb2O3 is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and even more preferably 0.1% or less. On the other hand, the lower limit of the content of S is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more, and the upper limit is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

[0049] When the sum of the contents of Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) exceeds 0%, it is effective to improve low-temperature melting property while reducing dispersion. Therefore, the lower limit of the sum of the contents of Rn2O components is preferably more than 0%, more preferably 1.0% or more, even more preferably 2.0% or more, even more preferably 3.0% or more, and even more preferably 4.0% or more. On the other hand, the total content of Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 28.0% or less in order to suppress deterioration of devitrification resistance and weather resistance. Therefore, the upper limit of the sum of the contents of the Rn2O component is preferably 28.0% or less, more preferably 25.0% or less, even more preferably 24.0% or less, and even more preferably 20.0% or less.

[0050] The total content of RO components (where R is one or more of MgO, CaO, SrO, and BaO) is preferably 5.0% or less to prevent a decrease in the stability of the glass and a deterioration in weather resistance. Therefore, the upper limit of the sum of the masses of RO components is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably 1.0% or less.

[0051] The Ln2O3 component (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is a component that increases the refractive index. The upper limit of the total content of the Ln2O3 component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and even more preferably 1.0% or less.

[0052] When the molar ratio (Al2O3 / P2O5) is 0.20 or more and 0.70 or less, the temperature coefficient of the relative refractive index can be increased while maintaining the optical properties of the glass, and deterioration of weather resistance due to the P2O5 component can be suppressed. Therefore, the lower limit of the molar ratio (Al2O3 / P2O5) is preferably 0.20 or more, more preferably 0.23 or more, even more preferably 0.25 or more, and even more preferably 0.27 or more. On the other hand, the upper limit of the molar ratio (Al2O3 / P2O5) is preferably 0.70 or less, more preferably 0.60 or less, even more preferably 0.50 or less, even more preferably 0.40 or less, even more preferably 0.38 or less, and even more preferably 0.35 or less.

[0053] By setting the molar ratio (Al2O3+RO+Li2O) / Al2O3 to 1.80 or less, it is possible to prevent deterioration in weather resistance. Therefore, the upper limit of the molar ratio (Al2O3+RO+Li2O) / Al2O3 is preferably 1.80 or less, more preferably 1.50 or less, even more preferably 1.30 or less, even more preferably 1.20 or less, and even more preferably 1.10 or less.

[0054] By setting the molar ratio (P2O5+RO+Li2O) / (P2O5-Al2O3) to 1.70 or less, it is possible to suppress devitrification during pressing and deterioration of weather resistance while maintaining optical properties. Therefore, the upper limit of the molar ratio (P2O5+RO+Li2O) / (P2O5-Al2O3) is preferably 1.70 or less, more preferably 1.65 or less, even more preferably 1.60 or less, even more preferably 1.58 or less, even more preferably 1.56 or less, and even more preferably 1.55 or less. On the other hand, by setting the molar ratio (P2O5+RO+Li2O) / (P2O5-Al2O3) to 1.30 or more, it is possible to improve the amount of Al2O3 component remaining undissolved during melting. Therefore, the lower limit of the molar ratio (P2O5+RO+Li2O) / (P2O5-Al2O3) is preferably 1.30 or more, more preferably 1.32 or more, even more preferably 1.33 or more, even more preferably 1.35 or more, even more preferably 1.38 or more, and even more preferably 1.40 or more.

[0055] Weather resistance can be improved when the molar ratio (ZrO2 / P2O5) exceeds 0. The lower limit of the molar ratio (ZrO2 / P2O5) is preferably greater than 0, more preferably 0.01 or more, and even more preferably 0.02 or more.

[0056] By setting the molar ratio (SiO2+B2O3) / Al2O3 to 0.40 or less, it is possible to increase the temperature coefficient of the relative refractive index while suppressing deterioration in weather resistance. Therefore, the upper limit of the molar ratio (SiO2+B2O3) / Al2O3 is preferably 0.40 or less, more preferably 0.38 or less, even more preferably 0.35 or less, even more preferably 0.31 or less, even more preferably 0.30 or less, even more preferably 0.25 or less, and even more preferably 0.23 or less.

[0057] In the present invention, it is preferable that the total content of the following components be 98.0% or more, 99.0% or more, 99.5% or more, and 99.8% or more in that order. P2O5 component, SiO2 component, B2O3 component, Al2O3 component, MgO component, CaO component, SrO component, BaO component, Li2O component, Na2O component, K2O component, La2O3 component, Y2O3 component, Gd2O3 component, Yb2O3 component, TiO2 component, Nb2O5 component, WO3 component, Bi2O3 component, ZnO component, ZrO2 component, Ta2O5 component, Sb2O3 component, F component.

[0058] <Ingredients that should not be included> Next, components that should not be contained in the optical glass of the present invention and components that are undesirable to contain will be explained.

[0059] Other components can be added as needed to the extent that they do not impair the properties of the glass of the present invention, but transition metal components such as Cu, Nd, Er, Cs, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo (excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu) tend to color the glass and absorb specific wavelengths in the visible range even when contained alone or in combination, even in small amounts. Therefore, it is preferable that they are substantially absent, particularly in optical glasses used with wavelengths in the visible range.

[0060] In this specification, "substantially free" preferably means that the content is less than 0.1%, and more preferably means that the content is free except for unavoidable impurities. Here, the content of components contained as unavoidable impurities is, for example, less than 0.01% or less than 0.001%, but is not limited thereto.

[0061] Furthermore, lead compounds such as PbO and arsenic compounds such as As2O3 are components that have a high environmental impact, so it is desirable to avoid their inclusion at all except in unavoidable cases.

[0062] Furthermore, in recent years, there has been a trend to reduce the use of Th, Cd, Tl, Os, Be, and Se components 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 commercialization. Therefore, when environmental impact is important, it is preferable that these components are substantially not contained.

[0063] <Physical properties> The physical properties of the optical glass of the present invention will now be described. The optical glass of the present invention preferably has a low refractive index and a high Abbe number (low dispersion). In particular, the refractive index (n d The lower limit of this refractive index (n d ) has an upper limit of preferably 1.55000 or less, more preferably 1.54500 or less, even more preferably 1.54000 or less, even more preferably 1.53500 or less, even more preferably 1.53000 or less, and even more preferably 1.52500 or less. In addition, the Abbe number (ν d The lower limit of this Abbe number (ν ) is preferably 60.00 or more, more preferably 63.00 or more, more preferably 64.00 or more, even more preferably 65.00 or more, even more preferably 65.50 or more, even more preferably 66.00 or more, and even more preferably 66.50 or more. d ) is preferably 80.00 or less, more preferably 75.00 or less as an upper limit, but is preferably 73.00 or less, more preferably 71.00 or less, even more preferably 70.50 or less, and even more preferably 70.00 or less as an upper limit. The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design, and in particular, it allows for miniaturization of the optical system while achieving high imaging characteristics, thereby expanding the degree of freedom in optical design.

[0064] The optical glass of the present invention has a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of 0×10 -6 (℃ -1 ) or more. In particular, the temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of the optical glass of the present invention is preferably 0×10 -6 (℃ -1 ) or more, more preferably 0.5 × 10 -6 (℃ -1 ) or more, more preferably 1.0 × 10 -6 (℃ -1 ) or above shall be the lower limit. The upper limit of the temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of the optical glass of the present invention is not particularly specified, but is preferably 10.0 × 10 -6 (℃ -1 ) or less, more preferably 8.0 × 10 -6 (℃ -1 ) or less, more preferably 7.0 × 10 -6 (℃ -1 ) or less, more preferably 6.0 × 10 -6 (℃ -1 ) or less, more preferably 4.5 × 10 -6 (℃ -1 ) or less. The optical glass of the present invention, which has such a temperature coefficient (40 to 60°C) of relative refractive index (589.29 nm), can be used to construct an optical system whose imaging characteristics are less affected by temperature fluctuations, and is therefore suitable for use as an optical element for in-vehicle applications and projectors. In the present invention, the temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) is sometimes referred to as "relative refractive index."

[0065] The optical glass of the present invention is characterized by its high weather resistance. When the glass surface deteriorates due to harsh environments, it can develop white tarnish, in which white speckled cloudiness appears on the glass surface, or blue tarnish, in which a blue-purple interference color appears, and the glass surface can also become sticky or prone to peeling. For example, in "JOGIS07:2019," the degree of weather resistance is measured by measuring the change in haze on the glass surface before and after the test. However, even if the change in haze is the same, it does not necessarily mean that the glass surface condition is the same. The whitening and bluening mentioned above are phenomena in which light appears scattered due to erosion of the glass surface or the deposition of reaction products on the glass surface, so it can be said that there is a correlation with the amount of change in haze. On the other hand, stickiness on the glass surface is caused by slight deterioration of the glass surface that is not enough to cause white or blue discoloration, and since the surface is transparent, the change in haze is very slight, but it can cause image distortion when used as an optical element. The glass of the present invention contains a large amount of the P2O5 component, and therefore has high water absorption due to the P2O5 component. Optical elements such as lenses are coated to prevent scratches on their surfaces. Coating refers to attaching a thin film to the surface of an optical element. When the surface of an optical element containing a large amount of the P2O5 component is coated, the coating easily peels off due to water absorption due to the P2O5 component, making it difficult to use the element as an optical element. Furthermore, glass whose surface is prone to peeling is affected by storage conditions such as temperature and humidity during storage location and transportation, making it difficult to use the glass as an optical element. The optical glass of the present invention has high weather resistance and is resistant to deterioration of the glass surface even in harsh environments, so that it can be used in a variety of situations.

[0066] [Manufacturing method] The optical glass of the present invention can be produced, for example, as follows: The above-mentioned raw materials are mixed uniformly so that the respective components fall within the prescribed content ranges, the mixture is placed in a platinum crucible, and the glass is produced according to a known glass production method depending on the degree of difficulty in melting the glass raw materials and the melting scale.

[0067] [Glass molding] The glass of the present invention can be melt-molded by known methods, but the means for shaping the glass melt is not limited.

[0068] [Optical elements] A glass molded body can be produced from the produced optical glass by, for example, polishing or mold press molding such as reheat press molding or precision press molding. That is, the glass molded body can be produced by subjecting the optical glass to mechanical processing such as grinding and polishing, or by precision press molding. However, the means for producing the glass molded body are not limited to these means. [Example]

[0069] The compositions of the examples and comparative examples of the glass of the present invention, the refractive index (n d ), Abbe number (ν d The results of the temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm), and the weather resistance test are shown in Tables 2 and 3. Comparative Example A is Example 16 of Patent Document 4 (WO2020 / 262014). Note that the following examples are for illustrative purposes only and are not limited to these examples.

[0070] For the glasses of the examples of the glass 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 these were weighed out and mixed uniformly to obtain the composition ratios of each example shown in the table. The mixture was then placed in a quartz 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 the mixture to remove bubbles, the temperature was lowered to 1000 to 1300°C, and the mixture was stirred and homogenized before being poured into a mold and slowly cooled to produce the glass.

[0071] The refractive index (n d ) is measured using the V-block method specified in JIS B 7071-2:2018 for the d-line (587.56 nm) of a helium lamp.d ) is the refractive index of the d line and the refractive index of the F line (486.13 nm) of a hydrogen lamp (n F ), refractive index for C line (656.27 nm) (n C ) value, the Abbe number (ν d )=[(n d -1) / (n F -n C )] was calculated using the formula:

[0072] The relative refractive index of the glass in the examples was measured by measuring the temperature coefficient of the relative refractive index at 40 to 60°C for light with a wavelength of 589.29 nm in accordance with the interference method specified in JIS B 7072-2:2020.

[0073] The weather resistance of the glasses of the Examples and Comparative Examples was tested by the following method. The glass used for the weather resistance test was 30 mm x 30 mm x 3 mm, and both sides were flat-polished to create a glass sample. This glass sample was placed in a small environmental test chamber (Espec Corporation, product number SH-641) within 24 hours of preparation and subjected to an environment of 70°C and 90% relative humidity for steps 1 to 3 in Table 1. After holding the sample in this environment of 70°C and 90% relative humidity for 150 hours (step 4), the temperature and humidity were lowered for steps 5 and 6, and the glass sample was removed and visually observed within 24 hours. Glass with no visible changes in condition on the polished surface is designated A, followed by glass with papule-like and tortoiseshell-like irregularities on the surface designated B, glass with fish-scale-like irregularities on the surface designated C, and glass with bark-like irregularities over the entire polished surface designated D.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] The optical glasses of the examples of the present invention all have a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of 0×10 -6 (℃ -1 ) and above.

[0078] Furthermore, the optical glasses of the examples have high weather resistance, and therefore are less susceptible to deterioration or clouding of the glass surface even in harsh environments.

[0079] Although the present invention has been described in detail for purposes of illustration, it will be understood that this is 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 invention.

Claims

1. The temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0x10 -6 (℃ -1 ) or more, In mole percent, Molar ratio (Al 2 O 3 / P 2 O 5 ) is 0.20 or more, P 2 O 5 The content of the ingredient is 47.0% or more, B 2 O 3 The content of the component is 4.0% or less, The total content of RO components (where R is one or more of MgO, CaO, SrO, and BaO) is 2.0% or less, the sum of the contents of Rn 2 O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is 9.60% or more and 28.0% or less; Molar ratio (P 2 O 5 +RO+Li 2 O) / (P 2 O 5 -Al 2 O 3 ) is 1.42 or more and 1.55 or less and Substantially free of Cu and Ag; Optical glass.

2. Refractive index (n ｄ ) is 1.45000 to 1.60000, and the Abbe number (ν ｄ 2. The optical glass according to claim 1, wherein σ is 60.00 to 80.

00.

3. An optical element made of the optical glass according to claim 1 or 2.

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