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 ZnO component of 6.0% or more and has a temperature coefficient (40-60°C) of a relative refractive index (589.29 nm) of 0×10-6 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 like digital cameras and video cameras, and image reproduction (projection) devices like 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 broadcast equipment are being used in more high-temperature environments. In such high-temperature environments, 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 more. At this time, since the adverse effects on the imaging characteristics and the like of the optical system due to temperature fluctuations become extremely large and cannot 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 hardly occurs, an optical element composed of glass whose refractive index decreases when the temperature rises and the temperature coefficient of the relative refractive index is negative, and an optical element composed of glass whose refractive index increases when the temperature becomes high and the temperature coefficient of the relative refractive index is positive are preferably used in combination, in that the influence on imaging characteristics and the like due to temperature changes can be corrected.

[0005] Here, as glasses developed focusing on the temperature coefficient of the 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

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The glass described in Patent Document 1 relates to a fluorophosphate-based glass focusing on the temperature coefficient of the relative refractive index, but the temperature coefficient of the relative refractive index only ranges from -3.8 to -2.3. Since the glass described in Patent Document 2 has a high transition point, its press formability is not good.

[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 relative refractive index of 0 or more, good press formability, 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 inventor has found that an optical glass can be obtained in which, 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 ZnO component is 6.0% or more, and the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more, and has thus completed the present invention. 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 ZnO component is 6.0% or more and contains The temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more optical glass.

[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 ZnO component is less than 6.0% the MgO component is more than 0%, contains, the mass sum Li2O×5 + Na2O + (K2O / 2) is more than 4.0%, the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or more optical glass.

[0012] (3) The optical glass according to (1) or (2), wherein the mass ratio Al2O3 / Rn2O is 0.5 or more (Rn is one or more selected from the group consisting of Li, Na, and K).

[0013] (4) The optical glass according to any one of (1) to (3), wherein the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is more than 0.

[0014] (5) The optical glass according to any one of (1) to (4), wherein the glass transition point (Tg) is 600 °C or less and the glass yield point (At) is 650 °C or less.

[0015] (6) An optical element made of the optical glass according to any one of (1) to (5).

[0016] (7) A preform for polishing and / or precision press forming made of the optical glass according to any one of (1) to (5).

Advantages of the Invention

[0017] According to the present invention, it is possible to provide an optical glass having good press formability and capable of contributing to the correction of the influence on imaging characteristics due to temperature changes, a preform, and an optical element using the same.

Embodiments for Carrying Out the Invention

[0018] 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. Note that, for parts where the description is repetitive, the description may be omitted as appropriate, but this does not limit the gist of the invention.

[0019] [Glass Components] The optical glass of the present invention has the forms of the first glass and the second glass. For each of the first glass and the second glass, the composition ranges of the respective components 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, assuming that oxides, double salts, metal fluorides, etc. used as raw materials for the glass constituent components of the present invention are all decomposed into oxides during melting, the total mass number of the generated oxides is set to 100 mass%, and each component contained in the glass is expressed.

[0020] <Regarding the Essential Components and Optional Components of the First Glass> 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 lowering the transition point. Therefore, the content of the P2O5 component is preferably 55.0% or more, more preferably 58.0% or more, still more preferably 60.0% or more, and most preferably 63.0% 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, still more preferably 78.0% or less, and most preferably 75.0% or less as the upper limit.

[0021] The Al2O3 component is an essential component of the present invention that increases the temperature coefficient of the relative refractive index. Therefore, the content of the Al2O3 component is preferably 3.0% or more, more preferably 4.0% or more, still more preferably 4.5% or more, even more preferably 5.0% or more, and most preferably 5.5% 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 and an increase in the transition point due to excessive content can be suppressed. Therefore, the content of the Al2O3 component is preferably 30.0% or less, more preferably 25.0% or less, still more preferably 20.0% or less, and most preferably 18.0% or less as the upper limit.

[0022] The ZnO component is an essential component of the present invention that can increase the temperature coefficient of the relative refractive index and meltability, and improve press formability. Although it is effective to contain the Rn2O component described later to improve press formability, the Rn2O component also reduces the relative refractive index. By setting the content of the ZnO component to 6.0% or more, equivalent meltability can be obtained. Therefore, the content of the ZnO component is preferably 6.0% or more, more preferably 6.5% or more, still more preferably 7.5% or more, and most preferably 8.0% or more as the lower limit. On the other hand, by setting the content of the ZnO component to 25.0% 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 25.0% or less, more preferably 22.0% or less, still more preferably 18.0% or less, even more preferably 15.0% or less, and most preferably 12.0% or less as the upper limit.

[0023] The MgO component is an optional component of the present invention that increases the temperature coefficient of the relative refractive index when the content is more than 0%. 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 0.5% or more, still more preferably 1.0% or more, and most preferably 1.5% or more as the lower limit. On the one hand, by setting the content of the MgO component to 10.0% 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 preferably has an upper limit of 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, and most preferably 4.0% or less.

[0024] 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 fusibility and increases the temperature coefficient of the relative refractive index. Therefore, the content of the CaO component preferably has a lower limit of 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. On the one hand, by setting the content of the CaO component to 10.0% or less, an increase in refractive index and dispersion can be suppressed. Therefore, the content of the CaO component preferably has an upper limit of 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.

[0025] When the SrO component is contained in an amount exceeding 0%, it is an optional component of the present invention that improves the low-temperature fusibility and increases the temperature coefficient of the relative refractive index. Therefore, the content of the SrO component preferably has a lower limit of 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. On the one hand, by setting the content of the SrO component to 10.0% or less, an increase in refractive index and dispersion can be suppressed. Therefore, the content of the SrO component preferably has an upper limit of 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.

[0026] When the BaO component is contained in an amount exceeding 0%, it is an optional component of the present invention that enhances the stability of the glass and increases the temperature coefficient of the relative refractive index. Therefore, the content of the BaO component preferably has a lower limit of 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. On the other hand, by setting the content of the BaO component to 15.0% or less, an increase in 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.

[0027] When the Li2O component contains more than 0%, it is an optional component that 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 other 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.

[0028] When the Na2O component contains more than 0%, it is an optional component that improves the low-temperature fusibility. 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 other 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.

[0029] When the K2O component contains more than 0%, it is an optional component that improves the low-temperature fusibility. 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 other 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.

[0030] When the content of the B2O3 component exceeds 0%, it is an optional component that promotes stable glass formation. On the other hand, if the B2O3 component is contained in excess, it causes devitrification of the glass and a decrease in the glass transition point. Therefore, the content of the B2O3 component is preferably 10.0% or less, more preferably 7.0% or less, still more preferably 4.0% or less, still more preferably 3.0% or less, and most preferably 1.0% or less as the upper limit.

[0031] When the content of the SiO2 component exceeds 0%, it is a glass-forming oxide component that can improve the viscosity of the molten glass. On the other hand, if the SiO2 component is contained in excess, it causes devitrification of the glass and a decrease in the glass transition point. 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.

[0032] When the content of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component exceeds 0%, they are optional components that can obtain 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.

[0033] When the TiO₂ component contains more than 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 achieve 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, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0034] When the Ta₂O₅ component contains more than 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 achieve 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, 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, the Ta₂O₅ component may not be contained.

[0035] When the WO₃ component contains more than 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 achieve 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, even more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0036] 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.

[0037] 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 obtain 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, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0038] 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 obtain 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, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0039] 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 obtain 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, 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, it is not necessary to contain the TeO2 component.

[0040] When the F component contains more than 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 one hand, by setting the content of the F component to 5.0% or less, it is possible to suppress the decrease in the temperature coefficient of the relative refractive index due to the F component. Therefore, the content of the F component is preferably 5.0% or less, 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.

[0041] The Sb2O3 component is an optional component that can defoam the molten glass when its content exceeds 0%. In particular, in the glass of the present invention, containing the Sb2O3 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 especially when used for optical elements for in-vehicle applications or projector applications. On the other hand, by setting the content of the Sb2O3 component to 1.0% or less, it is possible to suppress the decrease in transmittance in the short-wavelength region of the visible light region, solarization of the glass, and deterioration of the internal quality. Therefore, the content of the Sb2O3 component may be preferably 1.0% or less, more preferably less than 0.7%, still more preferably 0.4% or less, and most preferably 0.3% or less.

[0042] The sulfur (hereinafter referred to as S) component is an optional component that can defoam the molten glass when its content exceeds 0 ppm. 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 is preferably 1 ppm or more, more preferably 10 ppm or more, and still more preferably 20 ppm or more as the lower limit. 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 is preferably 300 ppm or less, more preferably 200 ppm or less, and still more preferably 100 ppm or less as the upper limit.

[0043] The Sb2O3 component and the S component can each obtain a defoaming effect when contained alone, but they may also 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 fusibility, which is crystals 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 and 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, and still more preferably 100 ppm or less as the upper limit.

[0044] 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 reducing dispersion while improving the low-temperature fusibility. 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 in excess, the devitrification resistance may deteriorate, so 15.0% or less is preferable. 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.

[0045] When the sum of the contents of RO components (where R is at least one 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 RO components 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, in order to suppress the decrease in the stability of the glass, the sum of the contents of RO components is preferably 20.0% or less. Therefore, the mass sum of RO components is preferably 20.0% or less, more preferably 18.0% or less, still more preferably 15.0% or less, and most preferably 12.0% or less as the upper limit.

[0046] When the sum of the contents of Ln2O3 components (where Ln is at least one 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 Ln2O3 components is preferably 10.0% or less, more preferably 7.0% 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 1.0% or less as the upper limit.

[0047] When the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is within a desired range, the temperature coefficient of the relative refractive index can be increased while reducing the specific gravity. Therefore, the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is preferably 1.00 or more, more preferably 1.50 or more, still more preferably 1.80 or more, still more preferably 2.00 or more, and most preferably 2.10 or more as the lower limit. On the other hand, the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is preferably 7.00 or less, more preferably 6.00 or less, still more preferably 5.50 or less, still more preferably 5.00 or less, and most preferably 4.50 or less as the upper limit.

[0048] By setting the sum of the masses of K₂O and Na₂O to 10.0% or less, the temperature coefficient of the relative refractive index can be increased. Therefore, the sum of the masses of K₂O and Na₂O preferably has an upper limit of 10.0% or less, more preferably 9.0% or less, and most preferably 8.0% or less.

[0049] When the mass ratio of Al₂O₃ / R₂O is 0.5 or more, the elution of the R₂O component after vitrification can be suppressed, and the temperature coefficient of the relative refractive index can be increased. Therefore, the mass ratio of Al₂O₃ / R₂O preferably has a lower limit of 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. On the other hand, by making the mass ratio of Al₂O₃ / R₂O infinite, the deterioration of devitrification resistance due to excessive addition of Al₂O₃ can be suppressed. Therefore, the mass ratio of Al₂O₃ / R₂O preferably has an upper limit of preferably infinite, more preferably 10.0 or less, more preferably 7.0 or less, still more preferably 5.0 or less, and most preferably 4.0 or less.

[0050] When the mass ratio of RO / (SiO₂ + B₂O₃ + P₂O₅ + R₂O) is within a desired range, the temperature coefficient of the relative refractive index can be increased while enhancing the fusibility. Therefore, the mass ratio of RO / (SiO₂ + B₂O₃ + P₂O₅ + R₂O) 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 of RO / (SiO₂ + B₂O₃ + P₂O₅ + R₂O) preferably has an upper limit of 0.90 or less, more preferably 0.70 or less, still more preferably 0.50 or less, still more preferably 0.30 or less, and most preferably 0.20 or less.

[0051] The Al₂O₃ component is a component that needs to be contained in order to improve the temperature coefficient of the relative refractive index. However, 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. The mass ratio of Al2O3 / (SiO2 + B2O3 + P2O5) is preferably greater than 0, more preferably 0.05 or more, still more preferably 0.08 or more, and most preferably greater than 0.10 as the lower limit. On the other hand, the mass ratio of Al2O3 / (SiO2 + B2O3 + P2O5) is preferably 1.0 or less, more preferably 0.8 or less, still more preferably 0.5 or less, and most preferably 0.3 or less as the upper limit.

[0052] 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.

[0053] <Regarding the essential components and optional components of the second glass> 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 lowering the transition point. Therefore, the content of the P2O5 component is preferably 55.0% or more, more preferably 58.0% or more, still more preferably 60.0% or more, and most preferably 63.0% 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, still more preferably 78.0% or less, and most preferably 75.0% or less as the upper limit.

[0054] The Al2O3 component is an essential component of the present invention that increases the temperature coefficient of the relative refractive index. Therefore, the content of the Al2O3 component is preferably 3.0% or more, more preferably 4.0% or more, still more preferably 4.5% or more, still more preferably 5.0% or more, and most preferably 5.5% 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 and an increase in the transition point due to excessive content can be suppressed. Therefore, the content of the Al2O3 component is preferably 30.0% or less, more preferably 25.0% or less, still more preferably 20.0% or less, and most preferably 18.0% or less as the upper limit.

[0055] The MgO component is an essential component of the present invention that 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, and can suppress a decrease in the relative refractive index even when the content of the ZnO component is small. Therefore, the content of the MgO component is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, and most preferably 1.2% or more as the lower limit. On the other hand, by setting the content of the MgO component to 10.0% 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 10.0% or less, more preferably 8.0% or less, still more preferably 7.0% or less, and most preferably 6.0% or less as the upper limit.

[0056] The ZnO component is an optional component of the present invention that can increase the temperature coefficient of the relative refractive index and the meltability when contained in an amount exceeding 0%. Therefore, the content of the ZnO component is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, still more preferably 2.0% or more, and most preferably 3.0% or more as the lower limit. On the other hand, by setting the content of the ZnO component to less than 6.0%, 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 less than 6.0%, more preferably 5.5% or less, still more preferably 5.0% or less, and most preferably 4.5% or less as the upper limit.

[0057] When the CaO component contains more than 0%, it is an optional component of the present invention that improves the low-temperature fusibility while increasing 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 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.

[0058] When the SrO component contains more than 0%, it is an optional component of the present invention that improves the low-temperature fusibility while increasing 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 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 2.0% or less as the upper limit.

[0059] When the BaO component contains more than 0%, it is an optional component of the present invention that enhances the stability of the glass while increasing 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 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.

[0060] When the Li₂O component contains more than 0%, it is an optional component for improving 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 other 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.

[0061] When the Na₂O component contains more than 0%, it is an optional component for improving the low-temperature fusibility. 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 other 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.

[0062] When the K₂O component contains more than 0%, it is an optional component for improving the low-temperature fusibility. 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.

[0063] When the content of the B2O3 component exceeds 0%, it is an optional component that promotes stable glass formation. On the one hand, when the B2O3 component is contained in excess, it causes devitrification of the glass and a decrease in the transition point. 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 3.0% or less, and most preferably 1.0% or less as the upper limit.

[0064] When the content of the SiO2 component exceeds 0%, it is a glass-forming oxide component that can improve the viscosity of the molten glass. On the one hand, when the SiO2 component is contained in excess, it causes devitrification of the glass and a decrease in the transition point. 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.

[0065] When the contents of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component exceed 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.

[0066] 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.

[0067] 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, it is not necessary to contain the Ta₂O₅ component.

[0068] 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.

[0069] When the ZrO₂ component is contained in an amount exceeding 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 obtain 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, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0070] 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, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0071] 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, still more preferably 2.0% or less, and most preferably less than 1.0% as the upper limit.

[0072] 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, 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 TeO2 component may not be contained.

[0073] When the F component contains more than 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 one hand, by setting the content of the F component to 5.0% or less, it is possible to suppress the decrease in the temperature coefficient of the relative refractive index due to the F component. Therefore, the content of the F component is preferably 5.0% or less, 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.

[0074] When the content of the Sb2O3 component exceeds 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 the fusibility, which is the crystal of platinum eroded from the crucible, can be achieved. Since the fusibility deteriorates the internal quality of the glass in the same way as bubbles, it becomes a problem particularly 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, it is possible to suppress the decrease in the transmittance in the short wavelength region of the visible light region, the solarization of the glass, and the deterioration of the internal quality. Therefore, the content of the Sb2O3 component may be preferably 1.0% or less, more preferably less than 0.7%, still more preferably 0.4% or less, and most preferably 0.3% or less.

[0075] When the content of sulfur (hereinafter referred to as S) component exceeds 0%, 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 is preferably 1 ppm or more, more preferably 10 ppm or more, and still more preferably 20 ppm or more as the lower limit. 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 is preferably 300 ppm or less, more preferably 200 ppm or less, and still more preferably 100 ppm or less as the upper limit.

[0076] The Sb2O3 component and the S component can each obtain a defoaming effect when contained alone, but they may also 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.

[0077] 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 reducing dispersion while improving the low-temperature meltability. 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 in excess, 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 8.0% or less as the upper limit.

[0078] When the sum of the contents of RO components (wherein R is at least one 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 RO components 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 RO components is preferably 20.0% or less in order to suppress the decrease in the stability of the glass. Therefore, the mass sum of RO components is preferably 20.0% or less, more preferably 18.0% or less, still more preferably 15.0% or less, and most preferably 12.0% or less as the upper limit.

[0079] When the sum of the contents of Ln2O3 components (wherein Ln is at least one 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 Ln2O3 components is preferably 10.0% or less, more preferably 7.0% 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 1.0% or less as the upper limit.

[0080] In the present invention, the glass transition point can be lowered by making the mass sum Li2O×5 + Na2O+(K2O / 2), which is obtained by adding the value obtained by multiplying the content of the Li2O component by 5, the content of the Na2O component, and the value obtained by halving the content of the K2O component, exceed 4.0%. Therefore, the mass sum Li2O×5 + Na2O+(K2O / 2) is preferably more than 4.0%, more preferably 4.5% or more, still more preferably 5.0% or more, and most preferably 5.5% or more as the lower limit.

[0081] When the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is within a desired range, the temperature coefficient of the relative refractive index can be increased while reducing the specific gravity. Therefore, the mass ratio (P2O5 + MgO) / (Al2O3 + ZnO) is preferably 1.00 or more, more preferably 1.50 or more, still more preferably 1.80 or more, still more preferably 2.00 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 10.00 or less, more preferably 9.00 or less, still more preferably 8.00 or less, still more preferably 7.50 or less, and most preferably 7.00 or less as the upper limit.

[0082] By setting the mass sum Ka2O + Na2O to 10.0% or less, the temperature coefficient of the relative refractive index can be increased. Therefore, the mass sum Ka2O + Na2O is preferably 10.0% or less, more preferably 9.0% or less, and most preferably 8.0% or less as the upper limit.

[0083] When the mass ratio 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. Therefore, the mass ratio Al2O3 / Rn2O is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 1.0 or more, still more preferably 1.2 or more, and most preferably 1.5 or more as the lower limit. On the other hand, by making the mass ratio Al2O3 / Rn2O infinite, the deterioration of devitrification resistance due to excessive addition of Al2O3 can be suppressed. Therefore, the mass ratio Al2O3 / Rn2O is preferably infinite, more preferably 8.0 or less, more preferably 6.0 or less, still more preferably 4.0 or less, and most preferably 3.0 or less as the upper limit.

[0084] When the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) is within a desired range, the melting property can be enhanced while increasing the temperature coefficient of the relative refractive index. Therefore, the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) is preferably more than 0, more preferably 0.01 or more, and most preferably 0.02 or more as the lower limit. On the other hand, the mass ratio RO / (SiO2 + B2O3 + P2O5 + Rn2O) is preferably 0.90 or less, more preferably 0.70 or less, still more preferably 0.50 or less, still more preferably 0.30 or less, and most preferably 0.20 or less as the upper limit.

[0085] The Al2O3 component is a component that needs to be contained in order to improve the temperature coefficient of the relative refractive index. However, depending on the ratio with the SiO2 component, B2O3 component, and P2O5 component, which are network-forming oxides, it may affect the meltability of the glass and the stability of the glass. The mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is preferably greater than 0, more preferably 0.05 or more, still more preferably 0.10 or more, and most preferably 0.12 or more as the lower limit. On the other hand, the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is preferably 1.0 or less, more preferably 0.8 or less, still more preferably 0.5 or less, and most preferably 0.3 or less as the upper limit.

[0086] 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.

[0087] <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.

[0088] Other components can be added as necessary within a range that does not impair the characteristics of the glass of the present application. 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 that even when contained in a small amount alone or in combination, the glass is colored and absorption occurs at a specific wavelength in the visible region. Therefore, in particular, in optical glass that uses wavelengths in the visible region, it is preferably not substantially contained.

[0089] In addition, "substantially free of" as used in this specification preferably means that the content is less than 0.1%, more preferably free of content except for inevitable impurities. Here, the content of components included as inevitable impurities is, for example, less than 0.01% or less than 0.001%, but is not limited thereto.

[0090] In addition, since lead compounds such as PbO and arsenic compounds such as As2O3 are components with high environmental loads, it is desirable to be completely free of them except for inevitable contamination.

[0091] Furthermore, each of the components of Th, Cd, Tl, Os, Be, and Se has recently tended to refrain from use as harmful chemical substances, and measures for environmental protection are required not only in the manufacturing process of glass but also in the processing process and disposal after productization. Therefore, when emphasizing environmental impact, it is preferable to be substantially free of these.

[0092] <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 preferably has a lower limit of 1.50000 or more, more preferably 1.51000 or more, and most preferably 1.52000 or more. On the other hand, this refractive index (n d ) preferably has an upper limit of 1.56000 or less, more preferably 1.55000 or less, still more preferably 1.54000 or less. In addition, the Abbe number (ν d ) of the optical glass of the present invention preferably has a lower limit of 60.00 or more, more preferably 62.00 or more, still more preferably 63.00 or more, and most preferably 64.00 or more. On the other hand, this Abbe number (ν d ) preferably has an upper limit of 75.00 or less, preferably 73.00 or less, more preferably 72.00 or less, and still more preferably 71.00 or less. 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, it is possible to miniaturize the optical system, thus expanding the degree of freedom in optical design.

[0093] The optical glass of the present invention preferably has a temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) of 0×10 -6 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 or more, more preferably 0.5×10 -6 or more, still more preferably 1.0×10 -6 or more as the lower limit. Also, although 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, it 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, and even more preferably 4.5×10 -6 or less. 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 are some places where the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is described as the relative refractive index.

[0094] The optical glass of the present invention preferably has a glass transition point (Tg) of 600 °C or lower. In particular, the glass transition point (Tg) of the optical glass of the present invention is preferably 600 °C or lower, more preferably 580 °C or lower, still more preferably 550 °C or lower, and most preferably 520 °C or lower as the upper limit. The optical glass of the present invention having such a glass transition point (Tg) is excellent in meltability, and thus can suppress devitrification during pressing.

[0095] The optical glass of the present invention preferably has a glass softening point (At) of 650°C or lower. In particular, the glass softening point (At) of the optical glass of the present invention preferably has an upper limit of 650°C or lower, more preferably 620°C or lower, still more preferably 600°C or lower, and most preferably 590°C or lower. The optical glass of the present invention having such a glass softening point (At) is excellent in meltability, so that devitrification during pressing can be suppressed.

[0096] 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 preferably has an upper limit of 3.50 or lower, more preferably 3.30 or lower, still more preferably 3.10 or lower, and most preferably 3.00 or lower. Such an optical glass with a low specific gravity is useful in optical design. In particular, since the size of the optical system can be reduced, the degree of freedom in optical design can be expanded.

[0097] [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 materials.

[0098] [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.

[0099] [Preform and optical element] A glass molded body can be produced from the produced optical glass by using, for example, means of grinding or means of mold pressing such as reheat press molding or precision press molding. That is, a glass molded body is produced by performing machining such as grinding and polishing on the optical glass, or a preform for mold pressing is produced from the optical glass, and after performing reheat press molding on this preform, polishing is performed to produce a glass molded body, or a preform produced by performing polishing, or a preform molded by known floating molding or the like is subjected to precision press molding to produce a glass molded body. Note that the means for producing the glass molded body is not limited to these means.

Examples

[0100] The compositions of the examples and comparative examples of the glass of the present invention, the refractive indices (n d ) of these glasses, the Abbe numbers (ν d ), the temperature coefficients (40 to 60 ° C) of the relative refractive index (589.29 nm), the transition points (Tg), the yield points (At), and the specific gravities are shown in Tables 1 to 4. Examples 1 to 7 are the first glass component, Examples 8 to 15 are the second glass component, Comparative Example A is Example 44 of WO2018 / 211861, and Comparative Example B is Example 12 of WO2007 / 049622. Note that the following examples are for illustrative purposes only and are not limited to these examples.

[0101] The glasses of the examples of the glass of the present invention were all selected from high-purity raw materials such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds that are usually used for optical glasses as raw materials for each component, weighed so as to have the composition ratios 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 to 1400 ° C for 1 to 5 hours according to the melting difficulty of the glass composition, stirred and homogenized to remove bubbles, etc., and then the temperature was lowered to 1000 to 1300 ° C, stirred and homogenized, and then cast into a mold and slowly cooled to produce glass.

[0102] The refractive index (n d) was shown as the measured value with respect to the d-line (587.56 nm) of the helium lamp in accordance with the V-block method specified 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 ) with respect to the F-line (486.13 nm) of the hydrogen lamp, and the refractive index (n C ) with respect to the C-line (656.27 nm) using the formula for the Abbe number (ν d ) = [(n d - 1) / (n F - n C )].

[0103] The relative refractive index of the glass of the example was measured for the value of 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.

[0104] The glass transition point (Tg) and yield point (At) of the glass of the example were determined from the thermal expansion curve obtained by measuring the relationship between temperature and the elongation of the sample in accordance with the Japan Optical Glass Industry Association Standard JOGIS08-2019 "Method for Measuring Thermal Expansion of Optical Glass".

[0105] The specific gravity in the glass of the example was determined based on the method for measuring density and specific gravity by the immersion method in liquid of JIS Z8807:2012.

[0106]

Table 1

[0107]

Table 2

[0108]

Table 3

[0109]

Table 4

[0110] The optical glasses of the embodiments of the present invention all have a temperature coefficient (40 - 60°C) of relative refractive index (589.29 nm) of 0×10 -6 or more.

[0111] Also, the optical glasses of the embodiments all had a glass transition point (Tg) of 600°C or less and a glass yield point (At) of 650°C or less.

[0112] Also, the optical glasses of the embodiments all had a specific gravity of 3.5 or less.

[0113] Also, the optical glasses of the embodiments formed stable glasses and were less likely to devitrify during glass production.

[0114] Therefore, the optical glasses of the embodiments 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 presumed that the optical glasses of the embodiments of the present invention can be suitably used in 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.

[0115] Furthermore, using the optical glasses of the embodiments 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.

[0116] As described above, the present invention has been described in detail for illustrative purposes. However, it should be understood that these embodiments are for illustrative purposes only, and those skilled in the art can make many modifications 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%, contains 6.0% or more of the ZnO component and Optical glass with a temperature coefficient (40 to 60 °C) of relative refractive index (589.29 nm) of 0×10 -6 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%, contains less than 6.0% of the ZnO component, more than 0% of the MgO component, and Mass and Li 2 O×5 + Na 2 O + (K 2 O / 2) exceeds 4.0%, An optical glass having a temperature coefficient (40 to 60 °C) of relative refractive index (589.29 nm) of 0×10 -6 or more.

3. Mass ratio of Al 2 O 3 / Rn 2 O is 0.5 or more (Rn is one or more selected from the group consisting of Li, Na, and K), the optical glass according to claim 1 or 2.

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

5. The optical glass according to any one of Claims 1 to 4, having a glass transition point (Tg) of 600°C or lower and a glass yield point (At) of 650°C or lower.

6. An optical element made of the optical glass according to any one of Claims 1 to 5.

7. A preform for polishing and / or precision press forming made of the optical glass according to any one of Claims 1 to 5.

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