Optical glass and optical elements

Abstract

To provide an optical glass in which the refractive index and Abbe number satisfy equation (1) and which has a low glass transition temperature. [Solution] In the glass composition expressed in mass%, the B2O3 content is 5.00% to 21.00%, the ZnO content is 6.50% or more, the La2O3 content is 25.00% to 40.00%, the Ta2O5 content is 5.00% to 18.00%, the WO3 content is 5.00% or less, the total content (SiO2 + B2O3 + P2O5) is 24.50% or less, and the total content (ZrO2 + Ta2O5 + Nb2O5 + Ti An optical glass having an O2+WO3 content of 12.00% or more, a mass ratio (SiO2 / B2O3) of 0.480 or less, a mass ratio (Li2O / SiO2) of 0.130 to 0.470, a mass ratio ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) of 2.150 or more, and satisfying equation (1): νd>-30.466×nd+97.760 for the refractive index nd and Abbe number νd.

Description

[Technical Field]

[0001] This invention relates to optical glass and optical elements. [Background technology]

[0002] In recent years, various types of optical glass have been proposed as materials for optical elements (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-201661 [Overview of the project] [Problems that the invention aims to solve]

[0004] Optical glass in which the refractive index and Abbe number satisfy a predetermined relationship is useful as a material for optical elements. For example, a concrete example of such a relationship is "Equation (1): νd > -30.466 × nd + 97.760".

[0005] Another desirable property for optical glass is a low glass transition temperature (Tg). Low-Tg glass is preferable because, for example, it has excellent suitability for precision pressing.

[0006] One aspect of the present invention aims to provide an optical glass in which the refractive index and Abbe number satisfy the above formula (1), and which has a low glass transition temperature. [Means for solving the problem]

[0007] One aspect of the present invention is as follows: [1] In glass composition expressed as mass%, B2O3 content is between 5.00% and 21.00%. ZnO content of 6.50% or more, La2O3 content is between 25.00% and 40.00%. Ta2O5 content is between 5.00% and 18.00%. WO3 content is 5.00% or less. The total content of SiO2, B2O3, and P2O5 (SiO2 + B2O3 + P2O5) is 24.50% or less. The total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 (ZrO2 + Ta2O5 + Nb2O5 + TiO2 + WO3) is 12.00% or more. The mass ratio of SiO2 content to B2O3 content (SiO2 / B2O3) is 0.480 or less. The mass ratio of Li2O content to SiO2 content (Li2O / SiO2) is between 0.130 and 0.470. The mass ratio of the total content of La2O3, Gd2O3, and Y2O3 to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is 2.150 or greater, and The refractive index nd and Abbe number νd are given by the following equation (1): νd>-30.466×nd+97.760 Optical glass that satisfies the requirements. [2] The optical glass described in [1], wherein the SiO2 content is 1.00% or more and 10.00% or less. [3] Optical glass as described in [1] or [2], wherein the Gd2O3 content is 12.00% or more and 23.00% or less. [4] Optical glass as described in any of [1] to [3], having a ZrO2 content of 2.00% or more. [5] Optical glass as described in any of [1] to [4], having a WO3 content of 4.30% or less. [6] An optical glass according to any of [1] to [5], wherein the mass ratio of SiO2 content to B2O3 content (SiO2 / B2O3) is 0.139 or more and 0.480 or less. [7] An optical glass according to any of [1] to [6], wherein the total content of Nb2O5, TiO2, and WO3 (Nb2O5 + TiO2 + WO3) is greater than 0.00% and less than or equal to 4.30%. [8] An optical glass according to any one of [1] to [7], wherein the mass ratio of the total content of ZrO2 and Ta2O5 to the total content of ZrO2, Ta2O5, Nb2O5, TiO2 and WO3 ((ZrO2+Ta2O5) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is 0.700 or more and 0.990 or less. [9] An optical glass according to any one of [1] to [8], wherein the mass ratio of the total content of La2O3, Gd2O3, and Y2O3 to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is 2.150 or more and 3.500 or less.

[10] An optical glass according to any of [1] to [9], wherein the glass transition temperature Tg is less than 610°C.

[11] The SiO2 content is 1.00% or more and 10.00% or less. The Gd2O3 content is between 12.00% and 23.00%. The ZrO2 content is 2.00% or more. The WO3 content is 4.30% or less. The mass ratio of SiO2 content to B2O3 content (SiO2 / B2O3) is between 0.139 and 0.480. The total content of Nb2O5, TiO2, and WO3 (Nb2O5 + TiO2 + WO3) is greater than 0.00% and less than or equal to 4.30%. The mass ratio of the total content of ZrO2 and Ta2O5 to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 ((ZrO2+Ta2O5) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is between 0.700 and 0.990. The mass ratio of the total content of La2O3, Gd2O3, and Y2O3 to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is 2.150 or more and 3.500 or less, and An optical glass according to any one of [1] to

[10] , having a glass transition temperature Tg of less than 610°C.

[12] An optical element made of the optical glass according to any one of [1] to

[11] .

Advantages of the Invention

[0008] According to one aspect of the present invention, an optical glass having a low glass transition temperature and useful optical constants as a material for an optical element can be provided. Further, according to one aspect of the present invention, an optical element made of such an optical glass can be provided.

Brief Description of the Drawings

[0009] [Figure 1] A schematic cross-sectional view of a precision press molding apparatus is shown.

Modes for Carrying Out the Invention

[0010] [Optical Glass] In the present invention and this specification, the glass composition is expressed as a glass composition on an oxide basis. Here, the "glass composition on an oxide basis" means a glass composition obtained by converting all the glass raw materials into oxides existing in the glass by decomposition during melting. Also, unless otherwise specified, the glass composition is expressed on a mass basis (mass%, mass ratio). The glass composition in the present invention and this specification can be determined by methods such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). For example, quantitative analysis is performed for each element using ICP-AES. Thereafter, the analysis values are converted into oxide notation. The analysis values by ICP-AES may include a measurement error of about ±5% of the analysis values, for example. Therefore, the values in oxide notation converted from the analysis values may also include an error of about ±5% similarly. Furthermore, in the present invention and this specification, a component content of 0.00% or not present or introduced means that the component is substantially absent, and that the component content is below the level of an impurity. Below the level of an impurity means, for example, less than 0.01%.

[0011] In the present invention and this specification, the refractive index refers to the refractive index nd at the helium d-line (wavelength 587.56 nm).

[0012] In the present invention and this specification, the Abbe number νd is used as a value that represents a property relating to variance, and is expressed by the following formula. νd=(nd-1) / (nF-nC) In the above formula, nF is the refractive index of blue hydrogen at the F line (wavelength 486.13 nm), and nC is the refractive index of red hydrogen at the C line (656.27 nm).

[0013] The optical glass (sometimes simply referred to as "glass") described above will be explained in more detail below.

[0014] <Glass composition> B2O3 is a network former and is a component that contributes to maintaining the thermal stability and fusion properties of the glass. Therefore, the B2O3 content is preferably 5.00% or more, and more preferably 7.00% or more, in the order of 8.00% or more, 9.00% or more, 10.00% or more, 10.50% or more, 11.00% or more, 11.50% or more, 12.00% or more, 12.50% or more, 13.00% or more, 13.25% or more, 13.50% or more, 13.75% or more, 14.00% or more, and 14.16% or more. B2O3 is also a component that, when present in larger amounts, leads to a lower refractive index of the glass. Therefore, the B2O3 content is preferably 21.00% or less, and more preferably 20.50% or less, in the order of 20.00% or less, 19.75% or less, 19.50% or less, 19.25% or less, 19.00% or less, 18.75% or less, 18.50% or less, 18.25% or less, and 18.05% or less.

[0015] SiO2 is also a network former and is a component that contributes to maintaining the thermal stability and melting properties of the glass. The SiO2 content can be 0.00% or more, and from the above point of view, it is preferably greater than 0.00%, and is more preferably in the order of 0.25% or more, 0.50% or more, 0.75% or more, 1.00% or more, 1.25% or more, 1.50% or more, 1.75% or more, 2.00% or more, 2.25% or more, and 2.44% or more. SiO2 is also a component that, when present in larger amounts, leads to a lower refractive index of the glass. Therefore, in the glass composition expressed as mass%, the SiO2 content is preferably 13.00% or less, and more preferably in the following order: 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.75% or less, 7.50% or less, 7.25% or less, 7.00% or less, 6.75% or less, 6.50% or less, 6.25% or less, 6.00% or less, 5.75% or less, 5.50% or less, 5.25% or less, and 5.21% or less.

[0016] P2O5 is also a network former and is a component that contributes to maintaining the thermal stability and fusion properties of glass. There is no particular lower limit to the P2O5 content, and it can be 0.00%, 0.00% or more, or greater than 0.00%. P2O5 is also a component that, when present in larger quantities, leads to a lower refractive index of the glass. Therefore, the P2O5 content is preferably 2.00% or less, and more preferably in the order of 1.50% or less, 1.00% or less, 0.90% or less, 0.80% or less, 0.70% or less, 0.60% or less, 0.50% or less, and 0.48% or less.

[0017] The total content of network formers (SiO2 + B2O3 + P2O5) is preferably 16.00% or more, and is more preferably 16.50% or more, 17.00% or more, 17.20% or more, 17.40% or more, 17.60% or more, 17.80% or more, 18.00% or more, 18.20% or more, and 18.22% or more, in that order. The upper limit is 24.50% or less from the viewpoint of maintaining high refractive index characteristics, and is preferably 24.00% or less, and is more preferably 23.50% or less, 23.00% or less, 22.80% or less, 22.60% or less, 22.50% or less, 22.40% or less, 22.30% or less, and 22.27% or less, in that order.

[0018] The mass ratio of SiO2 content to B2O3 content (SiO2 / B2O3) is preferably 0.025 or higher, and is more preferably 0.050 or higher, 0.060 or higher, 0.080 or higher, 0.100 or higher, 0.120 or higher, 0.139 or higher, 0.140 or higher, 0.160 or higher, 0.180 or higher, and 0.190 or higher, in that order. The upper limit is 0.480 or lower, preferably 0.460 or lower, and is more preferably 0.440 or lower, 0.420 or lower, 0.400 or lower, 0.380 or lower, 0.360 or lower, 0.355 or lower, 0.350 or lower, and 0.344 or lower, in that order. From the viewpoint of maintaining the thermal stability and high refractive index properties of the glass, the mass ratio (SiO2 / B2O3) is preferably within the above range.

[0019] The ZnO content is 6.50% or more, preferably 7.00% or more, and more preferably 8.00% or more, 8.50% or more, 9.00% or more, 9.25% or more, 9.50% or more, 9.75% or more, 10.00% or more, 10.25% or more, and 10.47% or more, in that order. There are no particular limitations on the upper limit; for example, values ​​are more preferable in the following order: 18.00% or less, 17.50% or less, 17.00% or less, 16.50% or less, 16.00% or less, 15.50% or less, 15.00% or less, 14.50% or less, 14.00% or less, 13.75% or less, 13.50% or less, 13.25% or less, and 13.04% or less. ZnO is a component that improves fusionability by lowering the glass transition temperature while suppressing the decrease in refractive index. On the other hand, if it is included in large quantities, the liquidus temperature will rise, reducing the thermal stability of the glass. From these viewpoints, the ZnO content is preferably within the above range.

[0020] Li2O is a component that can lower the glass transition temperature while suppressing the decrease in refractive index. The Li2O content can be 0.00% or more, preferably greater than 0.00%, and is more preferably 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, 0.60% or more, 0.70% or more, 0.80% or more, 0.90% or more, and 0.94% or more, in that order. From the viewpoint of the thermal stability of the glass, the upper limit of the Li2O content is preferably 4.00% or less, and is more preferably 3.00% or less, 2.80% or less, 2.60% or less, 2.40% or less, 2.20% or less, 2.00% or less, 1.80% or less, 1.60% or less, and 1.43% or less, in that order.

[0021] The mass ratio of Li2O content to SiO2 content (Li2O / SiO2) is 0.470 or less, with 0.460 or less, 0.450 or less, 0.440 or less, 0.430 or less, 0.420 or less, 0.410 or less, and 0.400 or less being preferred in that order. The lower limit is 0.130 or more, with 0.140 or more, 0.150 or more, 0.160 or more, 0.170 or more, 0.180 or more, and 0.190 or more being preferred in that order. Regarding the mass ratio (Li2O / SiO2), the lower limit is preferred from the viewpoint of lowering the glass transition temperature, and the upper limit is preferred from the viewpoint of suppressing the rise in the glass transition temperature and maintaining thermal stability.

[0022] The mass ratio of the total content of ZnO and Li2O to the SiO2 content ((ZnO+Li2O) / SiO2) is preferably 5.650 or less, and is more preferably 5.640 or less, 5.630 or less, 5.620 or less, 5.610 or less, 5.600 or less, 5.590 or less, 5.580 or less, 5.570 or less, and 5.569 or less, in that order. The lower limit is preferably 2.300 or more, and is more preferably 2.310 or more, 2.320 or more, 2.330 or more, 2.340 or more, 2.350 or more, 2.360 or more, 2.370 or more, 2.380 or more, 2.390 or more, 2.400 or more, 2.410 or more, 2.420 or more, and 2.430 or more, in that order. Regarding the mass ratio ((ZnO+Li2O) / SiO2), the lower limit is preferred from the viewpoint of lowering the glass transition temperature, and the upper limit is preferred from the viewpoint of suppressing the rise in the glass transition temperature and maintaining thermal stability.

[0023] The La2O3 content is 25.00% or more, preferably 25.25% or more, and more preferably 25.50% or more, 25.75% or more, 26.00% or more, 26.25% or more, and 26.46% or more, in that order. The La2O3 content is 40.00% or less, preferably 39.50% or less, and more preferably 38.00% or less, 37.75% or less, 37.50% or less, 37.25% or less, 37.00% or less, 36.80% or less, 36.60% or less, 36.40% or less, 36.20% or less, and 36.18% or less, in that order.

[0024] The Gd2O3 content can be 0.00%, 0.00% or more, or greater than 0.00%, with 4.00% or more being preferred, followed by 4.50% or more, 5.00% or more, 5.50% or more, 6.00% or more, 6.50% or more, 6.55% or more, 7.00% or more, 7.50% or more, 8.00% or more, 8.50% or more, 9.00% or more, 9.50% or more, 10.00% or more, 10.50% or more, 11.00% or more, 11.50% or more, 12.00% or more, 12.50% or more, 13.00% or more, 13.50% or more, 14.00% or more, 14.50% or more, and 15.00% or more, in that order of increasing preference. The upper limit is preferably 27.00% or less, and more preferably 26.00% or less, 25.00% or less, 24.50% or less, 24.00% or less, 23.50% or less, 23.00% or less, 22.50% or less, 22.00% or less, and 21.80% or less, in that order.

[0025] The Y2O3 content can be 0.00%, 0.00% or more, or greater than 0.00%. The upper limit is preferably 10.00% or less, with the following percentages being more preferable: 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, and 1.00% or less.

[0026] Regarding rare earth components, La2O3, Gd2O3, and Y2O3 are components that can increase the refractive index while maintaining low dispersibility, and from the viewpoint of maintaining or improving thermal stability, it is preferable that the content of each rare earth oxide be within the above range. Y2O3 has a smaller effect on increasing the refractive index compared to Gd2O3, which is also a rare earth component. Furthermore, if the total content of rare earth components becomes excessive, the thermal stability of the glass tends to decrease. Therefore, from the viewpoint of maintaining high refractive index characteristics while maintaining thermal stability, it is preferable to introduce La2O3 and / or Gd2O3 rather than Y2O3 as the rare earth component.

[0027] The ZrO2 content can be 0.00%, 0.00% or more, or greater than 0.00%, with the following preferences being in order: 1.00% or more, 1.25% or more, 1.50% or more, 1.75% or more, 2.00% or more, 2.16% or more, 2.25% or more, 2.50% or more, 2.70% or more, 2.90% or more, 3.00% or more, 3.25% or more, and 3.50% or more. The upper limit is preferably 8.00% or less, with the following preferences being in order: 7.50% or less, 7.00% or less, 6.75% or less, 6.50% or less, 6.25% or less, 5.00% or less, 5.75% or less, 5.50% or less, and 5.36% or less. Introducing ZrO2 into the glass is preferable because it improves the thermal stability of the glass without reducing its refractive index.

[0028] Ta2O5 is a component that maintains high refractive index, low dispersibility, and thermal stability. Therefore, the Ta2O5 content is 5.00% or more, preferably 5.25% or more, and more preferably 5.50% or more, 6.00% or more, 6.50% or more, 6.75% or more, 7.00% or more, 7.25% or more, 7.50% or more, 7.75% or more, 8.00% or more, 8.25% or more, 8.50% or more, and 8.81% or more, in that order. The upper limit is 18.00% or less, preferably 17.00% or less, and more preferably 16.50% or less, 16.00% or less, 15.75% or less, 15.50% or less, 15.25% or less, and 15.21% or less, in that order.

[0029] Nb2O5 is a component that increases the refractive index of glass, but if it is present in large quantities, it tends to reduce the thermal stability of the glass. The Nb2O5 content can be 0.00%, 0.00% or more, or greater than 0.00%, and is preferred in the order of 0.00% or more, 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, and 0.60% or more. The upper limit is preferably 5.00% or less, and is more preferably 4.00% or less, 3.50% or less, 3.00% or less, 2.80% or less, 2.60% or less, 2.40% or less, 2.20% or less, 2.00% or less, and 1.92% or less.

[0030] TiO2 is a component that increases refractive index and dispersion. However, excessive introduction of TiO2 tends to worsen the surface quality of the glass when it reacts with the molding surface of the mold during press molding, and may also cause the glass to become more discolored. Furthermore, the absence of TiO2 or its content being very low is preferable, for example, in precision press molding, from the viewpoint of suppressing the deterioration of the release film. From these viewpoints, the TiO2 content is preferably 0.60% or less, more preferably 0.40% or less, 0.30% or less, 0.20% or less, and 0.10% or less, in that order, and even more preferably 0.00% (i.e., no TiO2).

[0031] The WO3 content can be 0.00%, 0.00% or more, or greater than 0.00%, with the following preferences being 0.00% or more, 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, 0.60% or more, and 0.64% or more. The upper limit is 5.00% or less, with 4.90% or less being preferred, with the following preferences being 4.80% or less, 4.70% or less, 4.60% or less, 4.50% or less, 4.40% or less, 4.30% or less, 4.20% or less, 4.10% or less, and 4.09% or less. WO3 is a component that improves the thermal stability and meltability of glass and improves the refractive index. On the other hand, if it is included in large quantities, dispersion increases and the suitability for precision pressing decreases, so a smaller amount is preferable.

[0032] The total content of Nb2O5, TiO2, and WO3 (Nb2O5 + TiO2 + WO3) can be 0.00%, 0.00% or more, or greater than 0.00%, with the following preferences being in order: 0.00% or more, greater than 0.00%, 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, 0.60% or more, 0.70% or more, 0.80% or more, 0.90% or more, 1.00% or more, 1.10% or more, 1.20% or more, and 1.26% or more. The upper limit is preferably 5.00% or less, with the following preferences being in order: 4.90% or less, 4.80% or less, 4.70% or less, 4.60% or less, 4.50% or less, 4.40% or less, 4.30% or less, 4.20% or less, 4.10% or less, and 4.09% or less. The total content (Nb2O5 + TiO2 + WO3) is preferably at the lower limit mentioned above in order to improve thermal stability and meltability and enhance the refractive index. On the other hand, if it is included in large quantities, dispersion will increase and the suitability for precision pressing will decrease, so the upper limit mentioned above is preferable.

[0033] The total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 (ZrO2 + Ta2O5 + Nb2O5 + TiO2 + WO3) is 12.00% or more, and is preferred in the following order: 13.00% or more, 14.00% or more, 14.20% or more, 14.40% or more, 14.60% or more, 14.80% or more, 15.00% or more, 15.20% or more, 15.40% or more, 15.60% or more, 15.80% or more, 16.00% or more, and 16.26% or more. Regarding the upper limit, it is preferable that it be 25.00% or less, and more preferably in the following order: 24.50% or less, 24.00% or less, 23.50% or less, 23.00% or less, 22.50% or less, 22.00% or less, 21.80% or less, 21.60% or less, 21.40% or less, and 21.36% or less. The total content (ZrO2 + Ta2O5 + Nb2O5 + TiO2 + WO3) is preferably at the lower limit above in order to improve thermal stability and meltability and enhance the refractive index. On the other hand, if a large amount is included, dispersion will increase and the suitability for precision pressing will decrease, so the upper limit above is preferable.

[0034] The mass ratio of the total content of rare earth components La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 (ZrO2+Ta2O5+Nb2O5+TiO2+WO3) is ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+Ti The O2 + WO3 ratio is preferably 3.600 or less, and is preferred in the order of 3.500 or less, 3.450 or less, 3.400 or less, 3.350 or less, 3.330 or less, 3.250 or less, 3.200 or less, 3.150 or less, 3.100 or less, 3.090 or less, 3.080 or less, 3.070 or less, 3.060 or less, 3.050 or less, and 3.041 or less. The lower limit is 2.150 or more, and is preferred in the order of 2.160 or more and 2.185 or more. The mass ratio ((La2O3+Gd2O3+Y2O3) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is preferably within the above range from the viewpoint of maintaining high refractive index and low dispersion characteristics.

[0035] The mass ratio of the total content of ZrO2 and Ta2O5 (ZrO2 + Ta2O5) to the total content of ZrO2, Ta2O5, Nb2O5, TiO2, and WO3 (ZrO2 + Ta2O5 + Nb2O5 + TiO2 + WO3) ((ZrO2 + Ta2O5) / (ZrO2 + Ta2O5 + Nb2O5 + TiO2 + WO3) is preferably 1.000 or less, and is more preferably 0.995 or less, 0.990 or less, 0.985 or less, 0.980 or less, 0.975 or less, 0.970 or less, 0.965 or less, 0.960 or less, 0.955 or less, 0.950 or less, 0.945 or less, 0.940 or less, and 0.935 or less, in that order. The lower limit is preferably 0.700 or higher, and is more preferably 0.710 or higher, 0.720 or higher, 0.730 or higher, 0.740 or higher, 0.750 or higher, 0.760 or higher, 0.770 or higher, 0.775 or higher, 0.780 or higher, 0.785 or higher, and 0.788 or higher, in that order. The mass ratio ((ZrO2+Ta2O5) / (ZrO2+Ta2O5+Nb2O5+TiO2+WO3)) is preferably within the above range from the viewpoint of maintaining high refractive index characteristics and low dispersion characteristics.

[0036] Sb2O3 is a component that functions as a clarifying agent. The lower the amount added, the more preferable it is from the viewpoint of suppressing damage to the molding surface of the press molding die during precision press molding and suppressing discoloration of the glass. In the glass composition expressed in mass%, the Sb2O3 content expressed as an external division (Sb2O3 content when the total mass of glass components other than Sb2O3 is 100.00% by mass) is preferably 0.00% or more, 0.01% or more, and 0.02% or more, in that order, and more preferably 1.00% or less, 0.90% or less, 0.80% or less, 0.70% or less, 0.60% or less, and 0.50% or less, in that order.

[0037] <Glass Properties> (Formula (1)) In the optical glass described above, the refractive index nd and the Abbe number νd satisfy the following equation (1). Formula (1): νd>-30.466×nd+97.760 Optical glass that satisfies the above formula (1) exhibits low dispersion at a given refractive index and is useful as a material for optical elements. The optical glass described above preferably satisfies the following formula (1-1), and more preferably satisfies the following formula (1-2). Formula (1-1): νd>-30.466×nd+98.260 Formula (1-2): νd>-30.466×nd+98.460

[0038] (Glass transition temperature Tg) The optical glass described above can have a low glass transition temperature (Tg) due to its glass composition. Low-Tg glass is preferable, for example, in precision press molding, from the viewpoint of suppressing deterioration of the release film and suppressing wear of the press molding die. The Tg of the optical glass is preferably less than 610°C, and is more preferably 600°C or less, 598°C or less, 596°C or less, 594°C or less, 592°C or less, 590°C or less, 588°C or less, 586°C or less, 584°C or less, and 582°C or less, in that order. The lower limit of Tg is not particularly limited and can be, for example, 530°C or higher, and can be 540°C or higher, 550°C or higher, 560°C or higher, 562°C or higher, 564°C or higher, 566°C or higher, and 567°C or higher. The glass transition temperature (Tg) can be determined by the method described later.

[0039] (Refractive index nd) Since high refractive index glass is useful as a material for optical elements, the refractive index nd of the optical glass is preferably 1.82050 or higher, and is more preferably 1.82150 or higher, 1.82250 or higher, 1.82350 or higher, 1.82370 or higher, 1.82390 or higher, 1.82410 or higher, 1.82430 or higher, 1.82450 or higher, and 1.82476 or higher. The upper limit is preferably 1.85150 or lower, and is more preferably 1.85050 or lower, 1.84950 or lower, 1.84940 or lower, 1.84930 or lower, 1.84920 or lower, 1.84910 or lower, 1.84900 or lower, and 1.84892 or lower.

[0040] (Abbe number νd) Since low-dispersion glass is useful as a material for optical elements, the Abbe number νd of the above optical glass is preferably 41.50 or higher, and is more preferably 41.55 or higher, 41.60 or higher, 41.65 or higher, 41.70 or higher, 41.75 or higher, 41.80 or higher, 41.85 or higher, 41.90 or higher, and 41.92 or higher. The upper limit is preferably 43.80 or lower, and is more preferably 43.75 or lower, 43.70 or lower, 43.65 or lower, 43.60 or lower, 43.55 or lower, 43.50 or lower, and 43.46 or lower, in that order. When considering glass as a material for optical elements, increasing the refractive index of the glass corresponds to expanding the degrees of freedom of the glass. From the perspective of expanding the above-mentioned degrees of freedom, increasing the refractive index is preferable. On the other hand, when increasing the refractive index while maintaining the dispersion, there may be a tendency for the glass stability to decrease. From these perspectives, the Abbe number νd preferably falls within the above range.

[0041] (Coloration degree λ5, λ 80 ) The light transmittance of the glass, specifically, the suppression of the long-wavelength shift of the light absorption edge on the short-wavelength side can be evaluated by one or more of the coloration degrees λ5 and λ 80 . The coloration degree λ5 represents the wavelength at which the spectral transmittance (including surface reflection loss) of a 10-mm-thick glass becomes 5% from the ultraviolet region to the visible region. λ 80 represents the wavelength at which the spectral transmittance measured by the method described for λ5 becomes 80%. The λ5 and λ 80 shown in the table below are values measured in the wavelength range of 250 to 700 nm. The spectral transmittance T (%) of the glass in the present invention and this specification is for a glass sample having two optically polished parallel planes, and the intensity of light incident perpendicularly to one of these planes is I in , and the intensity of light emitted from the other side after passing through the glass sample is I out , when T (%) = I out / I in × 100 is represented. According to the coloration degrees λ5 and λ 80 , the absorption edge on the short-wavelength side of the spectral transmittance can be quantitatively evaluated. When joining lenses with an ultraviolet-curable adhesive for manufacturing a cemented lens, etc., ultraviolet light is irradiated through the optical element to cure the adhesive. From the perspective of efficiently curing the ultraviolet-curable adhesive, it is preferable that the absorption edge on the short-wavelength side of the spectral transmittance is in a short wavelength range. As an index for quantitatively evaluating this absorption edge on the short-wavelength side, one or more of the coloration degrees λ5 and λ 80 can be used. The optical glass described above can preferably exhibit a λ5 of 350 nm or less. λ5 is more preferably 345 nm or less, 340 nm or less, and 335 nm or less, in that order. Shorter wavelengths are more preferable for λ5, and there is no particular lower limit. The above optical glass preferably has a λ of 430 nm or less. 80 It can be shown that λ 80 The order of preference is 425 nm or less, 420 nm or less, 415 nm or less, and 410 nm or less. λ 80 Shorter wavelengths are more preferable, and there is no particular lower limit.

[0042] <Method of manufacturing glass> The optical glass described above can be obtained by weighing and blending raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides to obtain the desired glass composition, thoroughly mixing them to form a mixed batch, heating and melting it in a melting vessel, degassing and stirring to produce a homogeneous, bubble-free molten glass, and then shaping it. Specifically, it can be produced using known melting methods.

[0043] [Glass material for press molding, method for manufacturing the same, and method for manufacturing a glass molded product] According to one aspect of the present invention, a glass material for press molding made of the optical glass, a glass molded article made of the optical glass, and a method for manufacturing the same can be provided. Press-molded glass material refers to a block of glass that is heated and used for press molding. Examples of glass materials for press molding include glass blocks having a mass equivalent to the mass of the press-molded product, such as preforms for precision press molding and glass materials for press-molding optical element blanks (glass gobs for press molding). Glass materials for press molding can be produced through a process of processing glass molded bodies. Glass molded bodies can be produced by heating and melting glass raw materials as described above, and then molding the resulting molten glass. Examples of processing methods for glass molded bodies include cutting, grinding, and polishing.

[0044] [Optical element blanks and their manufacturing methods] According to one aspect of the present invention, an optical element blank made of the above-mentioned optical glass can be provided. The optical element blank is a glass molded body having a shape that approximates the shape of the optical element to be manufactured. The optical element blank can be manufactured by a method of molding glass to a shape that includes the shape of the optical element to be manufactured plus a processing allowance to be removed by processing. For example, the optical element blank can be manufactured by a method of heating and softening a glass material for press molding and then press molding it (reheat press method), or by a method of supplying a molten glass mass to a press molding die by a known method and then press molding it (direct press method).

[0045] [Optical elements and their manufacturing methods] According to one aspect of the present invention, an optical element made of the above-mentioned optical glass can be provided. Examples of types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, diffraction gratings, etc. Examples of lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, concave meniscus lenses, etc.

[0046] One method for manufacturing optical elements involves heating a preform for precision press molding and then precision press molding it. Known press molding dies and known molding methods can be used for precision press molding. This method of manufacturing optical elements by precision press molding is suitable for the production of aspherical lenses, microlenses, diffraction gratings, and the like.

[0047] It is preferable to coat the surface of a preform for precision press forming with a release film in order to prevent fusion between the glass and the molded surface of the press forming die during precision press forming, while ensuring good elongation of the glass along the molded surface. Such release films are well known. The optical glass is a low-Tg glass having a glass transition temperature within the range described above, and is glass that does not contain Ti or contains a small amount of Ti. A preform for precision press forming made of such glass is preferable from the viewpoint of suppressing deterioration of the release film. An example of a release film is a carbon-containing film. A carbon-containing film can be, for example, a film mainly composed of carbon (a film in which the carbon content is greater than the content of other elements when the elemental content in the film is expressed in atomic percent). As for the film formation method of the carbon-containing film, known methods such as vacuum deposition, sputtering, and ion plating using carbon raw materials, or known methods such as thermal decomposition using material gases such as hydrocarbons can be used.

[0048] Figure 1 shows a schematic cross-sectional view of a precision press forming apparatus. Precision press forming can be performed, for example, as follows. After placing the precision press molding preform (hereinafter simply referred to as "preform") 4 between the lower mold 2 and the upper mold 1 that constitute the press molding die, the inside of the quartz tube 11 is heated by energizing a heater (not shown) with a nitrogen atmosphere inside the quartz tube 11. The temperature inside the press molding die is adjusted so that the glass to be molded is, for example, 10 6 ~10 10 The temperature is set to one that exhibits a viscosity of dPa·s, and while maintaining this temperature, the push rod 13 is lowered to press the upper mold 1 and press the preform set in the mold. After pressing, the pressure is released, and with the press-formed glass product still in contact with the lower mold 2 and upper mold 1, the viscosity of the glass is set to, for example, 10 12The glass molded product is slowly cooled to a temperature of dPa·s or higher, then rapidly cooled to room temperature, and removed from the mold. In this way, an optical element can be obtained. In Figure 1, the holding member 10 holds the lower mold 2 and the body mold 3, and the support rod 9 supports the upper mold 1, lower mold 2, body mold 3, and holding member 10, and also receives the pressing pressure from the push rod 13. A thermocouple 14 is inserted inside the lower mold 2 to monitor the temperature inside the press mold.

[0049] Another method for manufacturing optical elements involves machining an optical element blank to produce the optical element. Examples of machining include cutting, shaping, rough grinding, fine grinding, and polishing. This manufacturing method is suitable for producing spherical lenses, prisms, and the like. [Examples]

[0050] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0051] [Examples No. 1 to No. 182] To achieve the glass composition shown in the table below, the corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc., were used as raw materials to introduce each component. The raw materials were weighed and thoroughly mixed to create the blended raw materials. In the table below, the glass composition is shown on a mass basis (mass %). The raw materials were placed in a platinum crucible and heated in a furnace set to 1250-1350°C for 120 minutes until melted. After stirring the molten glass to homogenize it, the molten glass was poured into a preheated mold, allowed to cool to near the glass transition temperature, and then immediately placed in an annealing furnace. It was held at approximately the glass transition temperature for about 30 minutes, then slowly cooled at a cooling rate of -30°C / hour for 4 hours, and then allowed to cool to room temperature in the furnace to obtain the optical glasses shown in the table below for Examples No. 1 to No. 182.

[0052] <Evaluation of physical properties> The physical properties of each optical glass shown in the table below were measured by the following method.

[0053] (1) Refractive index nd, Abbe number νd For each optical glass, the refractive index nd and Abbe number νd were measured according to the refractive index measurement method specified by the Nippon Optical Glass Manufacturers Association.

[0054] (2) Glass transition temperature Tg The glass was thoroughly crushed in a mortar and used as the sample. A platinum cell was used as the sample container, and the glass transition temperature (Tg) was measured using a differential scanning calorimetry analyzer (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10°C / min.

[0055] (3) Coloring degree λ5, λ 80 A glass sample with a thickness of 10 ± 0.1 mm and two opposing optically polished planes was used, and the spectral transmittance T (%) was measured using a spectrophotometer. The wavelength (nm) at which T was 5% was defined as λ5, and the wavelength (nm) at which T was 80% was defined as λ. 80 That's what I decided.

[0056] The results are shown in the table below. As shown in the table below, each optical glass from Examples No. 1 to No. 182 satisfies formula (1).

[0057] [Table 1-1]

[0058] [Table 1-2]

[0059] [Table 1-3]

[0060] [Table 1-4]

[0061] Table 1-5

[0062] Table 1-6

[0063] Table 1-7

[0064] Table 1-8

[0065] Table 1-9

[0066] Table 2-1

[0067] Table 2-2

[0068] Table 2-3

[0069] Table 2-4

[0070] Table 2-5

[0071] Table 2-6

[0072] Table 2-7

[0073] Table 2-8

[0074] Table 2-9

[0075] Table 3-1

[0076] Table 3-2

[0077] Table 3-3

[0078] Table 3-4

[0079] Table 3-5

[0080] Table 3-6

[0081] Table 3-7

[0082] Table 3-8

[0083] Table 3-9

[0084] Table 4-1

[0085] Table 4-2

[0086] Table 4-3

[0087] Table 4-4

[0088] Table 4-5

[0089] Table 4-6

[0090] Table 4-7

[0091] Table 4-8

[0092] [Table 4-9]

[0093] [Preparation of preforms for precision press molding] For each of the above examples, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials to introduce each component so that the glass composition shown in the table above would be obtained. The raw materials were weighed and thoroughly mixed to form the blended raw materials. Let's describe one example of preform fabrication (Example 1). The raw materials were placed in a platinum crucible, heated, and melted. The clarified and homogenized molten glass was discharged at a constant flow rate through a platinum alloy pipe, whose temperature was controlled to a range where stable discharge was possible without devitrification of the glass. The molten glass was then separated into molten glass lumps of the desired preform mass by a dripping or descent cutting method. The separated molten glass lumps were received in a mold with a gas nozzle at the bottom, and a preform for precision press molding was formed by ejecting gas from the nozzle to levitate the glass lumps. By adjusting and setting the separation interval of the molten glass lumps, a flattened spherical preform was obtained. Another example of preform production (Example 2) involves melting the raw materials to obtain homogeneous molten glass, which is then cast into a mold to form it. After that, the resulting molded body is deformed by annealing, cut or fractured to divide it into predetermined dimensions and shapes, producing multiple glass pieces. These glass pieces are then polished to smooth the surface, resulting in a preform made of glass of a predetermined mass. For the above embodiment, a preform for precision press molding was prepared according to Fabrication Example 2.

[0094] [Fabrication of optical elements] For each of the above embodiments, a carbon-containing film was coated onto the surface of the fabricated preform, and it was introduced into a press molding die including upper and lower molds and a body mold made of SiC, on which a carbon-containing release film was provided on the molding surface. The mold and preform were heated together in a nitrogen atmosphere to soften the preform, and then precision press-molded to produce various lenses (aspherical convex meniscus lenses, aspherical concave meniscus lenses, aspherical biconvex lenses, and aspherical biconcave lenses) made from the various types of glass. When the lenses produced in this way were observed, no scratches, haze, or damage were found on the lens surface.

[0095] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. For example, by performing the compositional adjustments described in the specification on the glass composition exemplified above, an optical glass according to one aspect of the present invention can be obtained. Furthermore, it is certainly possible to arbitrarily combine two or more items described as examples or preferred scopes in the specification.

Claims

1. In glass composition expressed as mass percent, B ２ O ３ The content is between 5.00% and 21.00%. ZnO content of 6.50% or more, La ２ O ３ The content is between 25.00% and 40.00%. Ta ２ O ５ The content is between 5.00% and 18.00%. WO ３ Content is 5.00% or less. SiO ２ 、 B ２ O ３ and P ２ O ５ The total content of (SiO ２ + B ２ O ３ + P ２ O ５ ) is 24.50% or less. ZrO ２ Ta ２ O ５ , Nb ２ O ５ , TiO ２ and WO ３ Total content (ZrO ２ +Ta ２ O ５ +Nb ２ O ５ +TiO ２ +WO ３ ) is 12.00% or more, B ２ O ３ SiO content ２ Mass ratio of content (SiO ２ / B ２ O ３ ) is 0.480 or less, SiO ２ Li content ２ O content mass ratio (Li ２ O / SiO ２ ) is between 0.130 and 0.

470. ZrO ２ Ta ２ O ５ , Nb ２ O ５ , TiO ２ and WO ３ La relative to the total content ２ O ３ , Gd ２ O ３ and Y ２ O ３ The total mass ratio of the content (La ２ O ３ +Gd ２ O ３ +Y ２ O ３ ) / (ZrO ２ +Ta ２ O ５ +Nb ２ O ５ +TiO ２ +WO ３ )) is 2.150 or higher, and The refractive index nd and Abbe number νd are given by the following equation (1): νd>-30.466×nd+97.760 Optical glass that satisfies the requirements.

2. SiO ２ The optical glass according to claim 1, wherein the content is 1.00% or more and 10.00% or less.

3. Gd ２ O ３ The optical glass according to claim 1, wherein the content is 12.00% or more and 23.00% or less.

4. ZrO ２ The optical glass according to claim 1, wherein the content is 2.00% or more.

5. WO ３ The optical glass according to claim 1, wherein the content is 4.30% or less.

6. B ２ O ３ SiO content ２ Mass ratio of content (SiO ２ / B ２ O ３ The optical glass according to claim 1, wherein the ratio is 0.139 or more and 0.480 or less.

7. Nb ２ O ５ , TiO ２ and WO ３ Total content (Nb ２ O ５ +TiO ２ +WO ３ The optical glass according to claim 1, wherein the amount of ) is greater than 0.00% and less than or equal to 4.30%.

8. ZrO ２ 、 Ta ２ O ５ 、 Nb ２ O ５ 、 TiO ２ and WO ３ The mass ratio of the total content of ZrO ２ and Ta ２ O ５ to the total content of (ZrO ２ + Ta ２ O ５ ) / (ZrO ２ + Ta ２ O ５ + Nb ２ O ５ + TiO ２ + WO ３ ) is 0.700 or more and 0.990 or less. The optical glass according to claim 1.

9. ZrO ２ Ta ２ O ５ , Nb ２ O ５ , TiO ２ and WO ３ La relative to the total content ２ O ３ , Gd ２ O ３ and Y ２ O ３ The total mass ratio of the content (La ２ O ３ +Gd ２ O ３ +Y ２ O ３ ) / (ZrO ２ +Ta ２ O ５ +Nb ２ O ５ +TiO ２ +WO ３ The optical glass according to claim 1, wherein the coefficient of the optical glass is 2.150 or more and 3.500 or less.

10. The optical glass according to claim 1, wherein the glass transition temperature Tg is less than 610°C.

11. SiO ２ The content is between 1.00% and 10.00%. Gd ２ O ３ The content is between 12.00% and 23.00%. ZrO ２ The content is 2.00% or more. WO ３ The content is 4.30% or less. B ２ O ３ SiO content ２ Mass ratio of content (SiO ２ / B ２ O ３ ) is between 0.139 and 0.480, Nb ２ O ５ , TiO ２ and WO ３ Total content (Nb ２ O ５ +TiO ２ +WO ３ ) is between 0.00% and 4.30%, ZrO ２ Ta ２ O ５ , Nb ２ O ５ , TiO ２ and WO ３ ZrO ２ and Ta ２ O ５ The mass ratio of the total content ((ZrO ２ +Ta ２ O ５ ) / (ZrO ２ +Ta ２ O ５ +Nb ２ O ５ +TiO ２ +WO ３ )) is between 0.700 and 0.990, ZrO ２ Ta ２ O ５ , Nb ２ O ５ , TiO ２ and WO ３ La relative to the total content ２ O ３ , Gd ２ O ３ and Y ２ O ３ The total mass ratio of the content (La ２ O ３ +Gd ２ O ３ +Y ２ O ３ ) / (ZrO ２ +Ta ２ O ５ +Nb ２ O ５ +TiO ２ +WO ３ )) is 2.150 or more and 3.500 or less, and The optical glass according to claim 1, wherein the glass transition temperature Tg is less than 610°C.

12. An optical element made of optical glass according to any one of claims 1 to 11.

Images