Optical glass, preform, and optical element

Abstract

To provide an optical glass that allows a temperature coefficient of a relative refractive index to take a value of 0 or more and can contribute to compensating for the effects of temperature changes on image-forming properties, and a preform and an optical element including the same.SOLUTION: An optical glass contains, on an oxide basis in mass%, a P2O5 component of 55.0-85.0%, an Al2O3 component of 3.0-30.0%, and a B2O3 component of 10.0% or less, and has a temperature coefficient (40-60°C) of a relative refractive index (589.29 nm) of 0×10-6 or more, the optical glass satisfying (a) or (b). (a) If the optical glass contains an MgO component, the mass ratio MgO / (CaO+SrO+BaO) is 0.10 or more. (b) If the optical glass does not contain a MgO component, the mass total CaO+SrO+BaO is 1.0% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to optical glass, preforms, and optical elements.

Background Art

[0002] In recent years, the digitalization and high definition of devices using optical systems have been rapidly progressing. In the fields of various optical devices such as imaging devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection TVs, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system and to reduce the weight and size of the entire optical system.

[0003] On the other hand, optical elements incorporated in in-vehicle optical devices such as in-vehicle cameras, and optical elements incorporated in many optical devices that generate a lot of heat such as projectors, copiers, laser printers, and broadcasting equipment are increasingly used in higher temperature environments. In such a high temperature environment, the temperature during use of the optical elements constituting the optical system is likely to vary greatly, and the temperature often reaches 100 ° C or higher. At this time, since the adverse effects on the imaging characteristics and the like of the optical system due to temperature fluctuations become too large to be ignored, it is required to configure an optical system in which the imaging characteristics and the like are hardly affected by temperature fluctuations.

[0004] In constructing an optical system in which the influence on imaging performance and the like due to temperature fluctuations is hardly generated, an optical element composed of glass having a refractive index that decreases when the temperature rises and a temperature coefficient of relative refractive index that is negative, and a temperature that increases when the temperature rises. It is preferable to use in combination an optical element composed of glass having a high refractive index and a positive temperature coefficient of relative refractive index in that it can correct the influence on imaging characteristics and the like due to temperature changes.

[0005] Here, as glass developed focusing on the temperature coefficient of relative refractive index, for example, glass compositions represented by Patent Documents 1 and 2 are known.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2020-132510 Patent Document 2 Japanese Patent Application Laid-Open No. 2019-182680 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The glasses described in Patent Documents 1 and 2 relate to phosphate glasses focusing on the temperature coefficient of the relative refractive index, and although glasses with a negative temperature coefficient of the relative refractive index are described, glasses with a temperature coefficient of the relative refractive index of 0 or more are not described. Specifically, the temperature coefficient of the relative refractive index of the fluorophosphate glass described in Patent Document 1 remains at -2.3 to -3.8, and the temperature coefficient of the relative refractive index of the P-Nb-based glass described in Patent Document 2 remains at -7.37 to -1.11.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical glass having a temperature coefficient of the relative refractive index of 0 or more and capable of contributing to the correction of the influence on imaging characteristics due to temperature changes, a preform using the same, and an optical element. MEANS FOR SOLVING THE PROBLEMS

[0009] As a result of intensive test research to solve the above problems, the present inventors have found that, in terms of mass% based on oxides, the P2O5 component is 55.0 to 85.0%, the Al2O3 component is 3.0 to 30.0%, and the B2O3 component is 10.0% or less, and the temperature coefficient (40 to 60 ° C) of the relative refractive index (589.29 nm) is 0×10 -6 or more, and an optical glass satisfying either (a) when containing an MgO component, the mass ratio MgO / (CaO+SrO+BaO) is 0.10 or more, or (b) when not containing an MgO component, the mass sum CaO+SrO+BaO is 1.0% or more can be obtained, and the present invention has been completed. Specifically, the present invention provides the following.

[0010] (1) In terms of mass % based on oxides, the P2O5 component is 55.0 to 85.0%, the Al2O3 component is 3.0 to 30.0%, the B2O3 component is 10.0% or less, contains, the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more, an optical glass satisfying either (a) or (b). (a) When containing the MgO component, the mass ratio MgO / (CaO + SrO + BaO) is 0.10 or more. (b) When not containing the MgO component, the mass sum CaO + SrO + BaO is 1.0% or more.

[0011] (2) In terms of mass % based on oxides, the P2O5 component is 55.0 to 85.0%, the Al2O3 component is 3.0 to 30.0%, the B2O3 component is 10.0% or less, the F component is more than 0 to 10.0% or less, contains, the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more, (a) or (b) an optical glass satisfying either. (a) When containing the MgO component, the mass ratio MgO / (CaO + SrO + BaO) is 0.10 or more. (b) When not containing the MgO component, the mass sum CaO + SrO + BaO is 1.0% or more.

[0012] (3) The optical glass according to (1) or (2), containing the Sb2O3 component and / or the S component.

[0013] (4) The optical glass according to any one of (1) to (3), wherein the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) of the total content of the P2O5 component and the MgO component to the total content of the Al2O3 component and the ZnO component is 2.50 to 9.00.

[0014] (5) The optical glass according to any one of (1) to (4), wherein the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is greater than 0.

[0015] (6) The optical glass according to any one of (1) to (5), wherein the grade based on JOGIS12 - 2012 "Method for Measuring Bubbles in Optical Glass" is from grade 1 to grade 3.

[0016] (7) An optical element made of the optical glass according to any one of (1) to (6).

[0017] (8) A preform for polishing and / or precision press forming made of the optical glass according to any one of (1) to (6).

Advantages of the Invention

[0018] According to the present invention, it is possible to provide an optical glass that can contribute to the correction of the influence on imaging characteristics due to temperature changes, and a preform and an optical element using the same.

Embodiments for Carrying Out the Invention

[0019] 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 implemented with appropriate modifications within the scope of the object of the present invention. In addition, regarding parts where the description overlaps, the description may be omitted as appropriate, but it does not limit the gist of the invention.

[0020] [Glass Components] The composition ranges of the respective components constituting the optical glass of the present invention are described below. In this specification, unless otherwise specified, the content of each component is expressed as mass% with respect to the total mass of the oxide-converted composition. Here, the "oxide-converted composition" is a composition in which each component contained in the glass is expressed assuming that oxides, double salts, metal fluorides, etc., used as raw materials for the glass components of the present invention are all decomposed into oxides upon melting. The total mass number of the resulting oxides is set to 100 mass%, and the total mass number of the resulting oxides is set to 100 mass%.

[0021] <Regarding essential components and optional components> The P2O5 component is an essential component of the present invention as a glass-forming oxide. In particular, by containing 55.0% or more of the P2O5 component, the stability of the glass can be enhanced while reducing the specific gravity. Therefore, the content of the P2O5 component is preferably 55.0% or more, more preferably 58.0% or more, still more preferably 59.0% or more, and most preferably 60.0% or more as the lower limit. On the other hand, by setting the content of the P2O5 component to 85.0% or less, devitrification of the glass can be reduced. Therefore, the content of the P2O5 component is preferably 85.0% or less, more preferably 82.0% or less, still more preferably 80.0% or less, and most preferably 78.0% or less as the upper limit.

[0022] The Al2O3 component is an essential component of the present invention that enhances the temperature coefficient of the relative refractive index. Therefore, the content of the Al2O3 component is preferably 3.0% or more, more preferably 5.0% or more, still more preferably 6.0% or more, still more preferably 7.0% or more, and most preferably 7.5% or more as the lower limit. On the other hand, by setting the content of the Al2O3 component to 30.0% or less, deterioration of devitrification resistance due to excessive content can be suppressed. Therefore, the content of the Al2O3 component is preferably 30.0% or less, more preferably 27.0% or less, still more preferably 25.0% or less, and most preferably 23.0% or less as the upper limit.

[0023] When the content of the F component exceeds 0%, it is an optional component that can obtain a defoaming effect while reducing dispersion. In particular, since the glass of the present invention contains a large amount of P2O5 component and Al2O3 component, bubbles tend to remain during melting. Therefore, the content of the F component is preferably more than 0%, more preferably 0.1% or more, still more preferably 0.2% or more, still more preferably 0.5% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by setting the content of the F component to 10.0% or less, a decrease in the temperature coefficient of the relative refractive index due to the F component can be suppressed. Therefore, the content of the F component is preferably 10.0% or less, more preferably 7.0% or less, still more preferably 5.0% or less, still more preferably 4.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably 1.5% or less as the upper limit.

[0024] When the MgO component is contained in an amount exceeding 0%, it is an optional component of the present invention that improves the low-temperature meltability and increases the temperature coefficient of the relative refractive index. The MgO component has the greatest effect of increasing the temperature coefficient of the relative refractive index among the RO components described later. Therefore, the content of the MgO component is preferably more than 0%, more preferably 1.0% or more, still more preferably 1.5% or more, and most preferably 2.0% or more as the lower limit. On the other hand, by setting the content of the MgO component to 12.0% or less, a decrease in devitrification resistance due to excessive content of the MgO component can be suppressed. Therefore, the content of the MgO component is preferably 12.0% or less, more preferably 10.0% or less, still more preferably 8.0% or less, and most preferably 6.0% or less as the upper limit.

[0025] When the CaO component is contained in an amount exceeding 0%, it is an optional component of the present invention that improves the low-temperature meltability and increases the temperature coefficient of the relative refractive index. Therefore, the content of the CaO component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by setting the content of the CaO component to 10.0% or less, an increase in the refractive index and dispersion can be suppressed. Therefore, the content of the CaO component is preferably 10.0% or less, more preferably 9.0% or less, still more preferably 7.0% or less, still more preferably 4.0% or less, and most preferably 3.0% or less as the upper limit.

[0026] The SrO component is an optional component of the present invention that, when contained in an amount exceeding 0%, improves the low-temperature fusibility and increases the temperature coefficient of the relative refractive index. Therefore, the content of the SrO component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by setting the content of the SrO component to 10.0% or less, an increase in the refractive index and dispersion can be suppressed. Therefore, the content of the SrO component is preferably 10.0% or less, more preferably 9.0% or less, still more preferably 7.0% or less, still more preferably 4.0% or less, and most preferably 3.0% or less as the upper limit.

[0027] The BaO component is an optional component of the present invention that, when contained in an amount exceeding 0%, enhances the stability of the glass and increases the temperature coefficient of the relative refractive index. Therefore, the content of the BaO component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by setting the content of the BaO component to 15.0% or less, an increase in the refractive index and dispersion can be suppressed. Therefore, the content of the BaO component is preferably 15.0% or less, more preferably 13.0% or less, still more preferably 11.0% or less, and most preferably 9.0% or less as the upper limit.

[0028] The Li2O component is an optional component that, when contained in an amount exceeding 0%, improves the low-temperature fusibility. Therefore, the content of the Li2O component is preferably more than 0%, more preferably 0.1% or more, still more preferably 0.3% or more, and most preferably 0.5% or more as the lower limit. On the one hand, by setting the content of the Li2O component to 10.0% or less, devitrification of the glass due to excessive content of the Li2O component can be suppressed. Therefore, the content of the Li2O component is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably 1.5% or less as the upper limit.

[0029] When the content of the Na2O component exceeds 0%, it is an optional component for improving the low-temperature meltability. Therefore, the content of the Na2O component is preferably more than 0%, more preferably 0.01% or more, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the one hand, by setting the content of the Na2O component to 15.0% or less, devitrification of the glass due to excessive content of the Na2O component can be suppressed. Therefore, the content of the Na2O component is preferably 15.0% or less, more preferably 12.0% or less, still more preferably 10.0% or less, still more preferably 8.0% or less, still more preferably 7.0% or less, and most preferably 5.5% or less as the upper limit.

[0030] When the content of the K2O component exceeds 0%, it is an optional component for improving the low-temperature meltability. Therefore, the content of the K2O component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the one hand, by setting the content of the K2O component to 15.0% or less, devitrification of the glass due to excessive content of the K2O component can be suppressed. Therefore, the content of the K2O component is preferably 15.0% or less, more preferably 12.0% or less, still more preferably 10.0% or less, still more preferably 8.0% or less, still more preferably 6.0% or less, and most preferably 5.5% or less as the upper limit.

[0031] When the ZnO component contains more than 0%, it is an optional component that increases the temperature coefficient of the relative refractive index. The content of the ZnO component is preferably more than 0%, more preferably 0.3% or more, still more preferably 0.5% or more, still more preferably 0.8% or more, still more preferably 1.0% or more, and most preferably 1.5% or more as the lower limit. On the other hand, by setting the content of the ZnO component to 10.0% or less, an increase in dispersion and a decrease in devitrification resistance due to excessive content can be suppressed. Therefore, the content of the ZnO component is preferably 10.0% or less, more preferably 9.0% or less, still more preferably 7.5% or less, still more preferably 5.5% or less, and most preferably 3.5% or less as the upper limit.

[0032] When the B2O3 component contains more than 0%, it is an optional component that promotes stable glass formation. On the other hand, when the B2O3 component is contained in excess, it causes devitrification of the glass. Therefore, the content of the B2O3 component is preferably 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, still more preferably 2.5% or less, and most preferably 1.0% or less as the upper limit.

[0033] When the SiO2 component contains more than 0%, it is a glass-forming oxide component that can improve the viscosity of the molten glass. On the other hand, when the SiO2 component is contained in excess, it causes devitrification of the glass. In particular, in the present invention, the SiO2 component is more likely to cause devitrification than the B2O3 component. Therefore, the content of the SiO2 component is preferably 10.0% or less, more preferably 7.0% or less, still more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably 1.0% or less as the upper limit.

[0034] When the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component contain more than 0%, they are optional components for obtaining a high refractive index. In particular, by setting the content of each of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component to 15.0% or less, a decrease in the Abbe number can be suppressed, devitrification can be reduced, and coloring can be reduced. Therefore, the content of each of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component is preferably 15.0% or less, more preferably 10.0% or less, still more preferably 8.0% or less, and most preferably 5.0% or less as the upper limit.

[0035] When the TiO2 component is contained in an amount exceeding 0%, it is an optional component that can increase the refractive index of the glass. When the content of the TiO2 component exceeds 10.0%, it becomes difficult to obtain the desired refractive index. Therefore, the content of the TiO2 component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0036] When the Ta2O5 component is contained in an amount exceeding 0%, it is an optional component that can increase the refractive index of the glass. When the content of the Ta2O5 component exceeds 10.0%, it becomes difficult to obtain the desired refractive index. Therefore, the content of the Ta2O5 component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit. From the perspective of reducing material costs, the Ta2O5 component may not be contained.

[0037] When the WO3 component is contained in an amount exceeding 0%, it is an optional component that can increase the refractive index of the glass. When the content of the WO3 component exceeds 10.0%, it becomes difficult to obtain the desired refractive index. Therefore, the content of the WO3 component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0038] When the ZrO₂ component contains more than 0%, it is an optional component that can increase the refractive index and dispersion of the glass. When the content of the ZrO₂ component exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the content of the ZrO₂ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0039] When the Nb₂O₅ component contains more than 0%, it is an optional component that can increase the refractive index and dispersion of the glass. When the content of the Nb₂O₅ component exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the content of the Nb₂O₅ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0040] When the Bi₂O₃ component contains more than 0%, it is an optional component that can increase the refractive index and lower the glass transition point. When the content of the Bi₂O₃ component exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the content of the Bi₂O₃ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0041] When the TeO₂ component contains more than 0%, it is an optional component that can increase the refractive index of the glass. When the content of the TeO₂ component exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the content of the TeO₂ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit. From the perspective of reducing material costs, it is not necessary to contain the TeO₂ component.

[0042] When the Sb₂O₃ component contains more than 0%, it is an optional component that can defoam the molten glass. In particular, in the glass of the present invention, when the Sb₂O₃ component is contained, not only the defoaming effect but also the improvement of fusibility, which is the crystal of platinum eroded from the crucible, can be achieved. Since fusibility deteriorates the internal quality of the glass in the same way as bubbles, it becomes a problem especially when used for optical elements for in-vehicle applications and projector applications. On the other hand, by setting the content of the Sb₂O₃ component to 1.0% or less, a decrease in transmittance in the short-wavelength region of the visible light region, solarization of the glass, and a decrease in internal quality can be suppressed. Therefore, the content of the Sb₂O₃ component may preferably be 1.0% or less, more preferably less than 0.7%, and even more preferably 0.4% or less.

[0043] When the sulfur (hereinafter referred to as S) component contains more than 0 ppm, it is an optional component that can defoam the molten glass. The S component is preferably contained, for example, by adding a sulfate component as a glass raw material. The sulfate component is, for example, one selected from lithium sulfate hydrate (Li₂SO₄·H₂O), sodium sulfate (Na₂SO₄), potassium sulfate (K₂SO₄), magnesium sulfate (MgSO₄), calcium sulfate hydrate (CaSO₄·1 / 2H₂O), strontium sulfate (SrSO₄), zinc sulfate hydrate (ZnSO₄·7H₂O), and lanthanum sulfate hydrate (La₂(SO₄)₃·9H₂O). The content of the S component preferably has a lower limit of 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more. On the other hand, by setting the content of the S component to 300 ppm or less, alloying and coloring when the S component is contained in excess can be prevented. Therefore, the content of the S component preferably has an upper limit of 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

[0044] The Sb2O3 component and the S component can each obtain a defoaming effect when contained alone, or they may be contained together. In particular, in the glass of the present invention, containing the Sb2O3 component and / or the S component can not only improve the defoaming effect, but also improve the fusibility which is the crystal of platinum eroded from the crucible. Since fusibility deteriorates the internal quality of the glass in the same way as bubbles, it becomes a problem when used for optical elements for in-vehicle applications or projector applications. When the Sb2O3 component and the S component are contained together, the content of the Sb2O3 component is preferably 0.5% or less, more preferably 0.3% or less, still more preferably 0.2% or less, and most preferably 0.1% or less. On the other hand, the content of the S component is preferably 1 ppm or more, more preferably 10 ppm or more, still more preferably 20 ppm or more as the lower limit, and preferably 300 ppm or less, more preferably 200 ppm or less, still more preferably 100 ppm or less as the upper limit.

[0045] When the sum of the contents of the Rn2O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) exceeds 0%, there is an effect of improving the low-temperature fusibility while reducing the dispersion. Therefore, the sum of the contents of the Rn2O component is preferably more than 0%, more preferably 1.0% or more, still more preferably 2.0% or more, and most preferably 2.5% or more as the lower limit. On the other hand, when the sum of the contents of the Rn2O component is contained excessively, the devitrification resistance may deteriorate. Therefore, it is preferably 15.0% or less. Therefore, the sum of the contents of the Rn2O component is preferably 15.0% or less, more preferably 12.0% or less, still more preferably 10.0% or less, and most preferably 9.0% or less as the upper limit.

[0046] When the sum of the contents of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) exceeds 0%, the low-temperature fusibility can be improved. Therefore, the sum of the contents of the RO component is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, still more preferably 1.5% or more, and most preferably 2.0% or more as the lower limit. On the other hand, the sum of the contents of the RO components is preferably 20.0% or less in order to suppress a decrease in the stability of the glass. Therefore, the mass sum of the RO components is preferably 20.0% or less, more preferably 18.0% or less, still more preferably 16.0% or less, and most preferably 15.5% or less as the upper limit.

[0047] When the sum of the contents of the Ln2O3 components (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) exceeds 0%, it is an optional component for obtaining a high refractive index. Therefore, the sum of the contents of the Ln2O3 components is preferably 15.0% or less, more preferably 10.0% or less, still more preferably 8.0% or less, still more preferably 6.0% or less, still more preferably 4.0% or less, and most preferably 1.5% or less as the upper limit.

[0048] When the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is within a desired range, it is possible to increase the temperature coefficient of the relative refractive index while reducing the specific gravity. Therefore, the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is preferably 2.50 or more, more preferably 2.60 or more, still more preferably 2.80 or more, still more preferably 2.90 or more, and most preferably 3.00 or more as the lower limit. On the other hand, the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is preferably 9.00 or less, more preferably 8.80 or less, still more preferably 8.50 or less, still more preferably 8.30 or less, and most preferably 8.00 or less as the upper limit.

[0049] When containing the MgO component, by setting the mass ratio MgO / (CaO + SrO + BaO) to be more than 0, it is possible to increase the temperature coefficient of the relative refractive index while reducing the specific gravity. Therefore, the mass ratio MgO / (CaO + SrO + BaO) is preferably 0.10 or more, more preferably 0.13 or more, and most preferably 0.15 or more as the lower limit.

[0050] When not containing the MgO component, by setting the mass sum of CaO + SrO + BaO to 1.0% or more, the temperature coefficient of the relative refractive index can be increased. In the present invention, among the RO components, the smaller the atomic number, the greater the effect of increasing the temperature coefficient of the relative refractive index. Therefore, the CaO component, SrO component, and BaO component tend to have a smaller effect of increasing the temperature coefficient of the relative refractive index compared to the MgO component. Accordingly, the mass sum of CaO + SrO + BaO is preferably 1.0% or more, more preferably 2.0% or more, still more preferably 3.0% or more, and most preferably 4.0% or more as the lower limit. On the other hand, since the mass sum of CaO + SrO + BaO will increase the specific gravity, it is preferably 15.0% or less. Accordingly, the mass sum of CaO + SrO + BaO is preferably 15.0% or less, more preferably 13.0% or less, still more preferably 11.0% or less, still more preferably 10.0% or less, and most preferably 9.0% or less as the upper limit.

[0051] By setting the mass sum of Ka2O + Na2O to 15.0% or less, the temperature coefficient of the relative refractive index can be increased. Accordingly, the mass sum of Ka2O + Na2O is preferably 15.0% or less, more preferably 12.0% or less, still more preferably 10.0% or less, still more preferably 9.0% or less, and most preferably 8.0% or less as the upper limit.

[0052] When the mass ratio (P2O5 + BaO) / (B2O3 + MgO) is 8.0 or more, the stability of the glass can be enhanced. Accordingly, the mass ratio (P2O5 + BaO) / (B2O3 + MgO) is preferably 8.0 or more, more preferably 10.0 or more, still more preferably 11.0 or more, still more preferably 12.0 or more, and most preferably 13.0 or more as the lower limit.

[0053] When the mass ratio of Al2O3 / Rn2O is 0.5 or more, the elution of the Rn2O component after vitrification can be suppressed, and the temperature coefficient of the relative refractive index can be increased. Accordingly, the mass ratio of Al2O3 / Rn2O is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.8 or more, still more preferably 0.9 or more, and most preferably 1.0 or more as the lower limit. On the other hand, by making the mass ratio Al2O3 / Rn2O infinite, it is possible to suppress the deterioration of devitrification resistance due to the excessive addition of Al2O3. Therefore, the mass ratio Al2O3 / Rn2O preferably has an upper limit of infinite, more preferably 15.0 or less, still more preferably 13.0 or less, even more preferably 10.0 or less, and most preferably 7.0 or less.

[0054] When the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) is within a desired range, it is possible to increase the fusibility while increasing the temperature coefficient of the relative refractive index. Therefore, the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) preferably has a lower limit of more than 0, more preferably 0.01 or more, and most preferably 0.02 or more. On the other hand, the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) preferably has an upper limit of 0.90 or less, more preferably 0.70 or less, still more preferably 0.50 or less, and most preferably 0.30 or less.

[0055] The Al2O3 component is a component that needs to be contained in order to improve the temperature coefficient of the relative refractive index, but depending on the ratio with the SiO2 component, B2O3 component, and P2O5 component, which are network-forming oxides, it may affect the fusibility and stability of the glass. When the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is more than 0, it is possible to increase the stability of the glass while improving the temperature coefficient of the relative refractive index. Therefore, the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) preferably has a lower limit of more than 0, more preferably 0.05 or more, still more preferably 0.08 or more, and most preferably more than 0.10. On the other hand, by making the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) 1.0 or less, it is possible to increase the fusibility and stability of the glass while suppressing the influence of the Al2O3 component. Therefore, the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) preferably has an upper limit of 1.0 or less, more preferably 0.8 or less, still more preferably 0.5 or less, and most preferably 0.3 or less.

[0056] In the present invention, it is preferable to contain the following components in total in the order of 98.0% or more, 99.0% or more, 99.5% or more, and 99.8% or more. 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.

[0057] <Regarding components that should not be contained> Next, components that should not be contained in the optical glass of the present invention and components that are preferably not contained will be described.

[0058] Other components can be added as necessary within a range that does not impair the properties of the glass of the present invention. However, each transition metal component such as Cu, Nd, Er, Cs, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, has the property of coloring the glass and causing absorption at specific wavelengths in the visible region even when contained in a small amount alone or in combination. Therefore, in optical glass that uses wavelengths in the visible region in particular, it is preferably not substantially contained.

[0059] Note that "substantially not contained" in this specification preferably means that the content is less than 0.1%, and more preferably not contained 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.

[0060] In addition, lead compounds such as PbO and arsenic compounds such as As2O3 are components with a high environmental load, so it is desirable not to contain any of them except for unavoidable contamination.

[0061] Furthermore, each of the components of Th, Cd, Tl, Os, Be, and Se has a tendency to refrain from being used as harmful chemical substances in recent years. Measures for environmental protection are required not only in the manufacturing process of glass but also in the processing process and the disposal after productization. Therefore, when emphasizing environmental impact, it is preferable that these are not substantially contained.

[0062] <Physical properties> The physical properties of the optical glass of the present invention will 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 ) of the optical glass of the present invention is preferably 1.45000 or more, more preferably 1.47000 or more, still more preferably 1.49000 or more, still more preferably 1.49500 or more, still more preferably 1.50000 or more, and most preferably 1.50500 or more as the lower limit. This refractive index (n d ) is preferably 1.55000 or less, more preferably 1.54500 or less, still more preferably 1.54000 or less, still more preferably 1.53500 or less, still more preferably 1.53000 or less, and most preferably 1.52500 or less as the upper limit. Also, the Abbe number (ν d ) of the optical glass of the present invention is preferably 63.00 or more, more preferably 64.00 or more, still more preferably 65.00 or more, still more preferably 65.50 or more, still more preferably 66.00 or more, and most preferably 66.50 or more as the lower limit. This Abbe number (ν d ) is preferably 75.00 or less as the upper limit, but preferably 73.00 or less, more preferably 71.00 or less, still more preferably 70.50 or less, and most preferably 70.00 or less as the upper limit. The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design. In particular, while achieving high imaging characteristics and the like, the miniaturization of the optical system can be achieved, so the degree of freedom in optical design can be expanded.

[0063] The optical glass of the present invention has a temperature coefficient (40 to 60 °C) of relative refractive index (589.29 nm) of 0 × 10-6 It is preferably as described above. 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 or more, more preferably 0.5×10 -6 or more, still more preferably 1.0×10 -6 or more as the lower limit. Also, 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 defined, but is preferably 10.0×10 -6 or less, more preferably 7.0×10 -6 or less, still more preferably 5.0×10 -6 or less, still more preferably 4.5×10 -6 or less may also be used. The optical glass of the present invention having such a temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) can form an optical system in which imaging characteristics and the like are hardly affected by temperature fluctuations, and thus can be suitably used for optical elements for in-vehicle applications and projector applications. In the present invention, there is a part where the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is described as "relative refractive index".

[0064] The optical glass of the present invention preferably has few bubbles in the glass. In particular, the grade of the cross-sectional area of the bubbles in the glass according to JOGIS12-2012 "Method for Measuring Bubbles in Optical Glass" is preferably grade 1 to 3, more preferably grade 1 to 2. Thereby, glass with good internal quality can be obtained, and image disturbance due to the influence of scattered light generated by the bubbles can be prevented.

[0065] The optical glass of the present invention preferably has a small specific gravity. In particular, the specific gravity of the optical glass of the present invention is preferably 3.50 or less, more preferably 3.30 or less, still more preferably 3.10 or less, and most preferably 3.00 or less as the upper limit. Such low-specific-gravity optical glass is useful in optical design. In particular, since it can reduce the weight of the optical system, it can expand the degree of freedom in optical design.

[0066] [Manufacturing method] The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible and produced according to a known glass manufacturing method according to the melting difficulty and melting scale of the glass raw material.

[0067] [Glass forming] The glass of the present invention can be melt-formed by a known method. The means for forming the glass melt is not limited.

[0068] [Preform and optical element] From the produced optical glass, a glass formed body can be produced by using, for example, means of polishing or means of mold press forming such as reheat press forming and precision press forming. That is, a glass formed body is produced by performing machining such as grinding and polishing on the optical glass, or a preform for mold press forming is produced from the optical glass, and after performing reheat press forming on this preform, polishing is performed to produce a glass formed body, or a preform produced by polishing or a preform formed by known floating forming or the like is subjected to precision press forming to produce a glass formed body. The means for producing the glass formed body is not limited to these means.

Examples

[0069] The compositions of the examples and comparative examples of the glass of the present invention, the refractive indices (n d ) and Abbe numbers (ν d) The temperature coefficient (40 - 60°C), specific gravity, and grades in the cross-sectional area of the bubbles of the relative refractive index (589.29 nm) are shown in Tables 1 - 2. The comparative example is Example 44 of WO2018 / 211861. 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 present invention, high-purity raw materials such as the corresponding oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc., which are usually used in optical glasses, were selected as raw materials for each component, weighed to obtain the proportions of the compositions of the respective examples shown in the table, and uniformly mixed. Then, they were put into a quartz crucible or a platinum crucible, melted in an electric furnace at a temperature range of 1100 - 1400°C for 1 - 5 hours according to the melting difficulty of the glass composition, stirred and homogenized to remove bubbles, etc. After that, the temperature was lowered to 1000 - 1300°C, stirred and homogenized, and then cast into a mold and slowly cooled to produce the glass.

[0071] The refractive index (n d ) of the glass of the example was shown as the measured value for the d-line (587.56 nm) of a helium lamp according to the V-block method defined in JIS B 7071-2:2018. Also, the Abbe number (ν d ) was calculated from the refractive index of the above d-line and the refractive indices (n F ) for the F-line (486.13 nm) of a hydrogen lamp and the refractive index (n C ) for the C-line (656.27 nm) using the formula for the Abbe number (ν d ) = [(n d - 1) / (n F - n C ).

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

[0073] The specific gravity in the glass of the example was measured based on the method for measuring density and specific gravity by the immersion method in liquid in JIS Z8807:2012.

[0074] The measurement of bubbles in the glass of the examples was carried out based on the Japan Optical Glass Industry Association Standard JOGIS12 - 2012 "Method for Measuring Bubbles in Optical Glass".

[0075] [Table 1]

[0076] [Table 2]

[0077] All of the optical glasses of the examples of the present invention had a temperature coefficient (40 - 60°C) of relative refractive index (589.29 nm) of 0×10 -6 or more.

[0078] Also, all of the optical glasses of the examples had a specific gravity of 3.5 or less.

[0079] Also, the optical glasses of the examples formed stable glasses and were less likely to devitrify during glass production.

[0080] Therefore, the optical glasses of the examples were optical glasses with a temperature coefficient (40 - 60°C) of relative refractive index (589.29 nm) of 0×10 -6 or more, few bubbles, and a small specific gravity. From this, it is inferred that the optical glasses of the examples of the present invention can be suitably used for in - vehicle cameras and projectors because they have a high temperature coefficient (40 - 60°C) of relative refractive index (589.29 nm) and good internal quality.

[0081] Furthermore, using the optical glasses of the examples of the present invention, a glass block was formed, and this glass block was ground and polished to be processed into the shapes of lenses and prisms. As a result, it was possible to stably process into various lens and prism shapes.

[0082] Although the present invention has been described in detail for illustrative purposes, it should be understood that these embodiments are for illustrative purposes only and that many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. In terms of mass% based on oxides, P 2 O 5 The content of the component is 55.0 to 85.0%, Al 2 O 3 The content of the component is 3.0 to 30.0%, B 2 O 3 The content of the component is 10.0% or less, containing The temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0 × 10 -6 or more, an optical glass satisfying either (a) or (b). When containing an MgO component, the mass ratio MgO / (CaO + SrO + BaO) is 0.10 or more. When not containing an MgO component, the sum of masses CaO + SrO + BaO is 1.0% or more.

2. In terms of mass% based on oxides, P 2 O 5 The content of the component is 55.0 to 85.0%, Al 2 O 3 The content of the component is 3.0 to 30.0%, B 2 O 3 The content of the component is 10.0% or less. containing an F component in an amount exceeding 0 to 10% or less, containing The temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more, an optical glass satisfying either (a) or (b). When containing an MgO component, the mass ratio MgO / (CaO + SrO + BaO) is 0.10 or more. When not containing an MgO component, the sum of masses CaO + SrO + BaO is 1.0% or more.

3. Sb 2 O 3 The optical glass according to claim 1 or 2, comprising an Sb component and / or an S component.

4. Al 2 O 3 The mass ratio of the total content of the P 2 O 5 component and the MgO component to the total content of the Al 2 O 5 +MgO) / (Al 2 O 3 +ZnO) is 2.50 to 9.

00. The optical glass according to any one of claims 1 to 3

5. Mass ratio of Al 2 O 3 / (SiO 2 +B 2 O 3 +P 2 O 5 The optical glass according to any one of claims 1 to 4, wherein the mass ratio of Al O / (SiO +B O +P O is greater than 0.

6. The optical glass according to any one of Claims 1 to 5, wherein the grade based on JOGIS12 - 2012 "Method for Measuring Bubbles in Optical Glass" is grade 1 to 3.

7. An optical element made of the optical glass according to any one of Claims 1 to 6.

8. A preform for polishing and / or precision press forming made of the optical glass according to any one of Claims 1 to 6.

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