Optical glass, preforms and optical elements

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 an optical glass, a preform, and an optical element. [Background technology]

[0002] In recent years, devices that use optical systems have rapidly become more digitalized and have higher definition. In the field of various optical devices, such as photographing devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions, there is a growing demand to reduce the number of optical elements, such as lenses and prisms, used in the optical system, and to make the entire optical system lighter and more compact.

[0003] On the other hand, optical elements incorporated in on-board optical devices such as on-board cameras and optical elements incorporated in optical devices that generate a lot of heat such as projectors, copy machines, laser printers, and broadcasting equipment are increasingly being used in higher temperature environments. In such high-temperature environments, the temperature of optical elements constituting the optical system is likely to fluctuate significantly during use, and in many cases the temperature reaches 100° C. or higher. In such cases, the adverse effect of temperature fluctuations on the imaging characteristics of the optical system becomes significant to a degree that cannot be ignored, so there is a demand for configuring an optical system whose imaging characteristics are less likely to be affected by temperature fluctuations.

[0004] In constructing an optical system that is less susceptible to the effects of temperature fluctuations on the imaging performance, etc., it is preferable to use in combination an optical element made of glass whose refractive index decreases as the temperature increases and whose temperature coefficient of the relative refractive index is negative, and an optical element made of glass whose refractive index increases as the temperature increases and whose temperature coefficient of the relative refractive index is positive, in order to correct the effects of temperature changes on the imaging performance, etc.

[0005] As glasses developed with a focus on the temperature coefficient of the relative refractive index, glass compositions such as those disclosed in Patent Documents 1 and 2 are known. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-132510 A [Patent Document 2] JP 2019-182680 A Summary of the Invention [Problem to be solved by the invention]

[0007] The glasses described in Patent Documents 1 and 2 relate to phosphate-based glasses that focus on the temperature coefficient of the relative refractive index, and although they describe glasses with a negative temperature coefficient of the relative refractive index, they do not describe glasses with a temperature coefficient of the relative refractive index of 0 or more. Specifically, the temperature coefficient of the relative refractive index of the fluorophosphate glass described in Patent Document 1 is only -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 is only -7.37 to -1.11.

[0008] The present invention has been made in consideration 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 equal to or greater than 0, and capable of contributing to correcting the effects of temperature changes on imaging characteristics, and a preform and optical element using the same. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors have conducted extensive testing and research, and as a result have discovered that a glass containing, in mass % on an oxide basis, 55.0 to 85.0% of a P2O5 component, 3.0 to 30.0% of an Al2O3 component, and 10.0% or less of a B2O3 component, and having a temperature coefficient (40 to 60°C) of a relative refractive index (589.29 nm) of 0×10 -6 The inventors have found that it is possible to obtain an optical glass which satisfies either (a) when the MgO component is contained, the mass ratio MgO / (CaO+SrO+BaO) is 0.10 or more, or (b) when the MgO component is not contained, the sum of the masses of CaO+SrO+BaO is 1.0% or more, and have completed the present invention. Specifically, the present invention provides the following:

[0010] (1) Mass percent based on oxides: P2O5 content: 55.0-85.0% Al2O3 content: 3.0-30.0% B2O3 content of 10.0% or less Contains The temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0×10 -6 That's all. Optical glass that satisfies either (a) or (b). (a) In the case where the MgO component is contained, the mass ratio MgO / (CaO+SrO+BaO) is 0.10 or more. (b) When the MgO component is not contained, the sum of the masses of CaO+SrO+BaO is 1.0% or more.

[0011] (2) Mass percent based on oxides: P2O5 content: 55.0-85.0% Al2O3 content: 3.0-30.0% B2O3 content of 10.0% or less F component is 0% or more and 10% or less. Contains The temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0×10 -6 That's all. Optical glass that satisfies either (a) or (b). (a) In the case where the MgO component is contained, the mass ratio MgO / (CaO+SrO+BaO) is 0.10 or more. (b) When the MgO component is not contained, the sum of the masses of CaO+SrO+BaO is 1.0% or more.

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

[0013] (4) The optical glass according to any one of (1) to (3), wherein the mass ratio of the total content of the P2O5 component and the MgO component to the total content of the Al2O3 component and the ZnO component, (P2O5+MgO) / (Al2O3+ZnO), 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) An optical glass according to any one of (1) to (5), which is graded 1 to 3 based on JOGIS12-2012 "Method of measuring bubbles in optical glass."

[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 molding, which is made of the optical glass according to any one of (1) to (6). Effect of the Invention

[0018] According to the present invention, it is possible to provide an optical glass that can contribute to correcting the effect of temperature changes on imaging characteristics, and a preform and an optical element that use the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the object of the present invention. Note that, although explanations of duplicated parts may be omitted as appropriate, this does not limit the gist of the invention.

[0020] [Glass components] The composition range of each component constituting the optical glass of the present invention is described below. In this specification, the content of each component is expressed as mass% relative to the total mass of the composition converted into oxides, unless otherwise specified. Here, the "composition converted into oxides" refers to a composition that expresses each component contained in the glass, assuming that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass components of the present invention are all decomposed and converted into oxides during melting, with the total mass number of the generated oxides being 100 mass%.

[0021] <Required and optional ingredients> 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 improved while the specific gravity can be reduced. Therefore, the lower limit of the content of the P2O5 component is preferably 55.0% or more, more preferably 58.0% or more, even more preferably 59.0% or more, and most preferably 60.0% or more. 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 upper limit of the content of the P2O5 component is preferably set to 85.0% or less, more preferably to 82.0% or less, further preferably to 80.0% or less, and most preferably to 78.0% or less.

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

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

[0024] The MgO component is an optional component of the present invention that, when contained at more than 0%, improves the low-temperature melting property while increasing the temperature coefficient of the relative refractive index. Among the RO components described below, the MgO component has the greatest effect of increasing the temperature coefficient of the relative refractive index. Therefore, the lower limit of the content of the MgO component is preferably more than 0%, more preferably 1.0% or more, even more preferably 1.5% or more, and most preferably 2.0% or more. On the other hand, by limiting the content of the MgO component to 12.0%, it is possible to prevent deterioration in devitrification resistance due to excessive inclusion of the MgO component. Therefore, the upper limit of the content of the MgO component is preferably 12.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and most preferably 6.0% or less.

[0025] The CaO component is an optional component of the present invention that, when contained at more than 0%, improves the low-temperature melting property while increasing the temperature coefficient of the relative refractive index. Therefore, the lower limit of the CaO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by keeping the CaO content at 10.0% or less, increases in the refractive index and dispersion can be suppressed. Therefore, the upper limit of the CaO content is preferably 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, even more preferably 4.0% or less, and most preferably 3.0% or less.

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

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

[0028] The Li2O component is an optional component that improves low-temperature melting property when it is contained at more than 0%. Therefore, the lower limit of the content of the Li2O component is preferably more than 0%, more preferably 0.1% or more, even more preferably 0.3% or more, and most preferably 0.5% or more. On the other hand, by keeping the content of the Li2O component at 10.0% or less, devitrification of the glass due to excessive inclusion of the Li2O component can be suppressed. Therefore, the upper limit of the content of the Li2O component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

[0029] The Na2O component is an optional component that improves low-temperature melting property when it is contained at more than 0%. Therefore, the lower limit of the Na2O content is preferably more than 0%, more preferably 0.01% or more, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by keeping the content of the Na2O component at 15.0% or less, devitrification of the glass due to excessive inclusion of the Na2O component can be suppressed. Therefore, the upper limit of the content of the Na2O component is preferably 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 7.0% or less, and most preferably 5.5% or less.

[0030] The K2O component is an optional component that improves low-temperature melting property when it is contained at more than 0%. Therefore, the lower limit of the content of the K2O component is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by keeping the content of the K2O component at 15.0% or less, devitrification of the glass due to excessive inclusion of the K2O component can be suppressed. Therefore, the upper limit of the content of the K2O component is preferably 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 6.0% or less, and most preferably 5.5% or less.

[0031] The ZnO component is an optional component that increases the temperature coefficient of the relative refractive index when it is contained at more than 0%. The lower limit of the content of the ZnO component is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, even more preferably 1.0% or more, and most preferably 1.5% or more. On the other hand, by keeping the content of the ZnO component at 10.0% or less, it is possible to suppress an increase in dispersion and a decrease in devitrification resistance due to an excessive content. Therefore, the upper limit of the content of the ZnO component is preferably 10.0% or less, more preferably 9.0% or less, even more preferably 7.5% or less, even more preferably 5.5% or less, and most preferably 3.5% or less.

[0032] The B2O3 component is an optional component that promotes stable glass formation when present at more than 0%. On the other hand, if the B2O3 component is contained in excess, it will cause devitrification of the glass, and therefore the upper limit of the B2O3 component content is preferably 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, even more preferably 2.5% or less, and most preferably 1.0% or less.

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

[0034] The La2O3 component, the Gd2O3 component, the Y2O3 component, and the Yb2O3 component are optional components that can provide a high refractive index when contained at more than 0%. In particular, by setting the content of each of the La2O3 component, the Gd2O3 component, the Y2O3 component, and the Yb2O3 component to 15.0% or less, the decrease in Abbe number can be suppressed, devitrification can be reduced, and coloring can be reduced. Therefore, the upper limit of each of the La2O3 component, the Gd2O3 component, the Y2O3 component, and the Yb2O3 component is preferably 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and most preferably 5.0% or less.

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

[0036] The Ta2O5 component is an optional component that can increase the refractive index of the glass when it is contained at more than 0%. If the content of the Ta2O5 component exceeds 10.0%, it becomes difficult to obtain the desired refractive index, so the content of the Ta2O5 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the Ta2O5 component may not be contained.

[0037] The WO3 component is an optional component that can increase the refractive index of the glass when it is contained at more than 0%. If the content of the WO3 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the upper limit of the content of the WO3 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

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

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

[0040] The Bi2O3 component is an optional component that can increase the refractive index and lower the glass transition point when it is contained in an amount exceeding 0%. If the content of the Bi2O3 component exceeds 10.0%, it becomes difficult to achieve the desired refractive index, so the content of the Bi2O3 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0041] The TeO2 component is an optional component that can increase the refractive index of the glass when it is contained at more than 0%. If the content of the TeO2 component exceeds 10.0%, it becomes difficult to obtain a desired refractive index, so the content of the TeO2 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the TeO2 component may not be contained.

[0042] The Sb2O3 component is an optional component that can defoam the glass melt when it is contained at more than 0%. In particular, when the glass of the present invention contains the Sb2O3 component, it not only has a defoaming effect, but also improves knots, which are platinum crystals eroded from the crucible. Knots deteriorate the internal quality of the glass in the same way as bubbles, and are therefore problematic when the glass is used for optical elements for in-vehicle applications or projectors. On the other hand, by making the content of Sb2O3 component 1.0% or less, it is possible to suppress the decrease in 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 Sb2O3 component may be preferably 1.0% or less, more preferably less than 0.7%, and further preferably 0.4% or less.

[0043] The sulfur (hereinafter referred to as S) component is an optional component that can defoam the molten glass when the content exceeds 0 ppm. The S component is preferably added, 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 lower limit of the content of the S component is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more. On the other hand, by keeping the S content at 300 ppm or less, it is possible to prevent alloying and coloring that would occur if the S content were excessively high, and therefore the upper limit of the S content is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

[0044] Although the Sb2O3 component and the S component each have a defoaming effect even when contained alone, they may be contained together. In particular, when the glass of the present invention contains the Sb2O3 component and / or the S component, not only is the defoaming effect achieved, but also knots, which are platinum crystals eroded from the crucible, can be improved. Knots deteriorate the internal quality of the glass in the same way as bubbles, and are therefore problematic when the glass is used in optical elements for in-vehicle applications or projectors. When Sb2O3 and S are contained together, the content of Sb2O3 is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and most preferably 0.1% or less. On the other hand, the content of S is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more as the lower limit, and preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less as the upper limit.

[0045] When the sum of the contents of Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) exceeds 0%, it has the effect of improving low-temperature melting property while reducing dispersion. Therefore, the lower limit of the sum of the contents of Rn2O components is preferably more than 0%, more preferably 1.0% or more, even more preferably 2.0% or more, and most preferably 2.5% or more. On the other hand, the sum of the contents of the Rn2O components is preferably 15.0% or less because excessive content may deteriorate devitrification resistance. Therefore, the upper limit of the sum of the contents of the Rn2O components is preferably 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, and most preferably 9.0% or less.

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

[0047] 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) is an optional component that can provide a high refractive index when it exceeds 0%. Therefore, the upper limit of the sum of the contents of the Ln2O3 components is preferably 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 4.0% or less, and most preferably 1.5% or less.

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

[0049] When the MgO component is contained, the specific gravity can be reduced while increasing the temperature coefficient of the relative refractive index by making the mass ratio MgO / (CaO+SrO+BaO) greater than 0. Therefore, the lower limit of 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.

[0050] When the MgO component is not contained, the temperature coefficient of the relative refractive index can be increased by making the mass sum CaO+SrO+BaO 1.0% or more. In the present invention, the smaller the atomic number of the RO component, the greater the effect of increasing the temperature coefficient of the relative refractive index, so the CaO component, the SrO component, and the BaO component tend to have a smaller effect of increasing the temperature coefficient of the relative refractive index than the MgO component. Therefore, the lower limit of the mass sum CaO+SrO+BaO is preferably 1.0% or more, more preferably 2.0% or more, even more preferably 3.0% or more, and most preferably 4.0% or more. On the other hand, the mass sum of CaO+SrO+BaO is preferably 15.0% or less because the specific gravity is large. Therefore, the upper limit of the mass sum of CaO+SrO+BaO is preferably 15.0% or less, more preferably 13.0% or less, even more preferably 11.0% or less, even more preferably 10.0% or less, and most preferably 9.0% or less.

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

[0052] When the mass ratio (P2O5+BaO) / (B2O3+MgO) is 8.0 or more, the stability of the glass can be improved. Therefore, the mass ratio (P2O5+BaO) / (B2O3+MgO) is preferably 8.0 or more, more preferably 10.0 or more, even 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 Al2O3 / Rn2O is 0.5 or more, it is possible to suppress the dissolution of the Rn2O component after vitrification and to increase the temperature coefficient of the relative refractive index. Therefore, the lower limit of the mass ratio Al2O3 / Rn2O is preferably 0.5 or more, more preferably 0.7 or more, even more preferably 0.8 or more, even more preferably 0.9 or more, and most preferably 1.0 or more. On the other hand, by making the mass ratio Al2O3 / Rn2O infinite, it is possible to suppress deterioration of devitrification resistance due to excessive addition of Al2O3. Therefore, the mass ratio Al2O3 / Rn2O is preferably set to infinity, and its upper limit is more preferably 15.0 or less, 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 temperature coefficient of the relative refractive index while improving the melting property. Therefore, the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) has a lower limit of preferably more than 0, more preferably 0.01 or more, and most preferably 0.02 or more. On the other hand, the upper limit of the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.50 or less, and most preferably 0.30 or less.

[0055] The Al2O3 component needs to be included in order to improve the temperature coefficient of the relative refractive index, but depending on the ratio with the network-forming oxides SiO2, B2O3, and P2O5, it may affect the meltability and stability of the glass. The stability of the glass can be enhanced while improving the temperature coefficient of the relative refractive index when the mass ratio Al2O3 / (SiO2+B2O3+P2O5) is greater than 0. Therefore, the lower limit of the mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably greater than 0, more preferably 0.05 or more, even more preferably 0.08 or more, and most preferably greater than 0.10. On the other hand, by setting the mass ratio Al2O3 / (SiO2+B2O3+P2O5) to 1.0 or less, the meltability and stability of the glass can be improved while suppressing the effects of the Al2O3 component. Therefore, the upper limit of the mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably set to 1.0 or less, more preferably to 0.8 or less, even more preferably to 0.5 or less, and most preferably to 0.3 or less.

[0056] In the present invention, it is preferable that the total content of the following components is 98.0% or more, 99.0% or more, 99.5% or more, and 99.8% or more in that order. P2O5 component, SiO2 component, B2O3 component, Al2O3 component, MgO component, CaO component, SrO component, BaO component, Li2O component, Na2O component, K2O component, La2O3 component, Y2O3 component, Gd2O3 component, Yb2O3 component, TiO2 component, Nb2O5 component, WO3 component, Bi2O3 component, ZnO component, ZrO2 component, Ta2O5 component, Sb2O3 component, F component.

[0057] <Ingredients that should not be included> Next, components that should not be contained in the optical glass of the present invention and components whose inclusion is undesirable will be described.

[0058] Other components may be added as necessary to the extent that they do not impair the properties of the glass of the present invention. However, transition metal components such as Cu, Nd, Er, Cs, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, have the property that even when contained alone or in combination in small amounts, the glass is colored and absorbs at specific wavelengths in the visible range, so it is preferable that they are not substantially contained in optical glasses that use wavelengths in the visible range, particularly.

[0059] In this specification, "substantially free" preferably means that the content is less than 0.1%, and more preferably means that the content is free except for unavoidable impurities. Here, the content of components contained as unavoidable impurities is, for example, less than 0.01% or less than 0.001%, but is not limited thereto.

[0060] Furthermore, since lead compounds such as PbO and arsenic compounds such as As2O3 are components that have a high environmental impact, it is desirable to avoid their inclusion at all except in unavoidable cases.

[0061] Furthermore, in recent years, there has been a trend to refrain from using the components Th, Cd, Tl, Os, Be, and Se as harmful chemical substances, and environmental measures are required not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Therefore, when environmental impact is important, it is preferable that these components are not substantially contained.

[0062] <Physical Properties> The physical properties of the optical glass of the present invention will now be described. The optical glass of the present invention preferably has a low refractive index and a high Abbe number (low dispersion). In particular, the refractive index (n d The lower limit of this refractive index (n d ) is preferably 1.55000 or less, more preferably 1.54500 or less, even more preferably 1.54000 or less, even more preferably 1.53500 or less, even more preferably 1.53000 or less, and most preferably 1.52500 or less. In addition, the Abbe number (ν d The lower limit of this Abbe number (ν d ) is preferably upper limit of 75.00 or less, more preferably upper limit of 73.00 or less, more preferably upper limit of 71.00 or less, even more preferably upper limit of 70.50 or less, and most preferably upper limit of 70.00 or less. The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design, and in particular allows the optical system to be made compact while achieving high imaging characteristics, thereby expanding the freedom of optical design.

[0063] The optical glass of the present invention has a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of 0×10-6 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 More preferably, 0.5×10 -6 More preferably, 1.0×10 -6 The above is the lower limit. The upper limit of the temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) of the optical glass of the present invention is not particularly specified, but is preferably 10.0×10 -6 Less than or equal to 7.0×10 -6 Less than 5.0×10, more preferably -6 Less than 4.5×10, more preferably -6 The following may also be used. The optical glass of the present invention, which has such a temperature coefficient (40 to 60°C) of relative refractive index (589.29 nm), can be used to configure an optical system whose imaging characteristics are unlikely to be affected by temperature fluctuations, and can therefore be suitably used as an optical element for in-vehicle applications or projectors. In the present invention, the temperature coefficient (40 to 60° C.) of the relative refractive index (589.29 nm) is sometimes referred to as the "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 ​​bubbles in the glass according to JOGIS12-2012 "Method of measuring bubbles in optical glass" is preferably 1 to 3, more preferably 1 to 2. This makes it possible to obtain glass with good internal quality and prevents image distortion caused by the influence of scattered light caused by bubbles.

[0065] The optical glass of the present invention preferably has a low specific gravity. In particular, the upper limit of the specific gravity of the optical glass of the present invention is preferably 3.50 or less, more preferably 3.30 or less, even more preferably 3.10 or less, and most preferably 3.00 or less. Such optical glass with a low specific gravity is useful in optical design, and in particular allows the optical system to be made lighter, thereby expanding the degree of freedom in optical design.

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

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

[0068] [Preforms and optical elements] From the produced optical glass, a glass molded body can be produced, for example, by using a polishing means or a mold press molding means such as reheat press molding or precision press molding. That is, a glass molded body can be produced by performing mechanical processing such as grinding and polishing on the optical glass, a preform for mold press molding can be produced from the optical glass, and the preform can be subjected to reheat press molding and then polished to produce a glass molded body, or a preform produced by polishing or a preform molded by known floating molding can be subjected to precision press molding to produce a glass molded body. Note that the means for producing a glass molded body are not limited to these means. EXAMPLES

[0069] The compositions of the examples and comparative examples of the glass of the present invention, the refractive indexes of these glasses (n d ), Abbe number (ν d), temperature coefficient (40 to 60°C) of relative refractive index (589.29 nm), specific gravity, and grade in cross-sectional area of ​​the foam are shown in Tables 1 and 2. The comparative example is Example 44 of WO2018 / 211861. Note that the following examples are merely for illustrative purposes and are not limited to these examples.

[0070] For the glasses of the examples of the glass of the present invention, high purity raw materials used in ordinary optical glass, such as the corresponding oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, were selected as the raw materials for each component, weighed out to obtain the composition ratio of each example shown in the table, and mixed uniformly. The mixture was then placed in a quartz crucible or a platinum crucible and melted in an electric furnace at a temperature range of 1100 to 1400°C for 1 to 5 hours depending on the melting difficulty of the glass composition. After stirring and homogenizing the mixture and removing bubbles, the temperature was lowered to 1000 to 1300°C and the mixture was stirred and homogenized, and the mixture was poured into a mold and slowly cooled to produce the glass.

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

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

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

[0074] Measurement of bubbles in the glass in the examples was carried out based on the Japan Optical Glass Industry Association standard JOGIS12-2012 "Method of measuring bubbles in optical glass."

[0075] [Table 1]

[0076] [Table 2]

[0077] The optical glasses according to the embodiments of the present invention all have a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of 0×10 -6 That was all.

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

[0079] Furthermore, the optical glasses of the Examples formed stable glasses, and devitrification was unlikely to occur during the glass production.

[0080] Therefore, the optical glass of the embodiment has a temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) of 0×10 -6 The optical glass had few bubbles and a low specific gravity. From this, it is presumed that the optical glass of the embodiment of the present invention has a high temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) and good internal quality, and therefore can be suitably used for in-vehicle cameras and projectors.

[0081] Furthermore, a glass block was formed using the optical glass of the embodiment of the present invention, and the 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 the glass block into various shapes of lenses and prisms.

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

Claims

1. In mass% based on oxide, P 2 O 5 Ingredients: 55.0-85.0%, A 2 O 3 Ingredients: 10.97-30.0%, F component: 0% to 10% Contains B 2 O 3 The component is 10.0% or less, Contains no Cu component except for unavoidable impurities. The temperature coefficient (40 to 60°C) of the relative refractive index (589.29 nm) is 0x10 -6 That's all. An optical glass that satisfies either (a) or (b). (a) In the case where the MgO component is contained, the mass ratio MgO / (CaO+SrO+BaO) is 0.13 or more. (b) When the MgO component is not contained, the mass sum of CaO+SrO+BaO is 3.0% or more.

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

3. A 2 O 3 The ratio of P to the total content of the 2 O 5 The mass ratio of the total content of the component and the MgO component (P 2 O 5 + MgO) / (Al 2 O 3 3. The optical glass according to claim 1, wherein the refractive index (ZnO) is 2.50 to 8.

00.

4. Mass ratio Al 2 O 3 / (SiO 2 +B 2 O 3 +P 2 O 5 4. The optical glass according to claim 1, wherein the refractive index is 0.17 or more.

5. 5. The optical glass according to claim 1, which is rated as grade 1 to 3 based on JOGIS12-2012 "Method of measuring bubbles in optical glass."

6. An optical element comprising the optical glass according to any one of claims 1 to 5.

7. A preform for polishing and / or precision press molding, which is made of the optical glass according to any one of claims 1 to 5.

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