Halide glass and optical element

Abstract

Provided are a halide glass having dispersion characteristics comparable to that of fluorite, and an optical element. The halide glass contains, in mol%, 15% to less than 29% of AlF3, 5% to 40% of YF3, and 26% to 80% of MgF2 + CaF2 + SrF2 + BaF2.

Description

Technical Field

[0001] The present invention relates to halide glass and optical elements. Background Art

[0002] In an optical system such as a camera, in order to correct chromatic aberration, a lens made of a low-dispersion material is used. For example, as a representative low-dispersion material, fluorite is known.

[0003] On the other hand, fluorite lacks formability and workability, and it takes a lot of time and cost to manufacture a lens. Therefore, as an alternative material to fluorite, for example, halide glasses such as fluoride glass and fluorophosphate glass having an Abbe number (νd) comparable to that of fluorite have been studied (Patent Documents 1 and 2).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-151493

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2016-023111 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] In addition to low dispersion, fluorite exhibits a high partial dispersion ratio (abnormal partial dispersibility). Therefore, halide glasses having dispersion characteristics comparable to those of fluorite are not known, and further research is needed.

[0010] In view of the above circumstances, an object of the present invention is to provide a halide glass and an optical element having dispersion characteristics comparable to those of fluorite.

[0011] Technical Means for Solving the Problem

[0012] Each embodiment of the halide glass for solving the above problems will be described.

[0013] The halide glass of Embodiment 1 is characterized by containing, in mol%, AlF3 of 15% to less than 29%, YF3 of 5% to 40%, and MgF2 + CaF2 + SrF2 + BaF2 of 26% to 80%. Here, "MgF2 + CaF2 + SrF2 + BaF2" means the total amount of MgF2, CaF2, SrF2, and BaF2.

[0014] For the halide glass of Embodiment 2, it is preferably that in Embodiment 1, AlF3 / YF3 is 5 or less. Here, "AlF3 / YF3" means a value obtained by dividing the content of AlF3 by the content of YF3.

[0015] For the halide glass of Mode 3, it is preferably that in Mode 1 or Mode 2, it contains, in mol%, MgF2 11% to 24%, CaF2 8% to 33%, SrF2 0% to 23%, and BaF2 7% to 20%.

[0016] For the halide glass of Mode 4, it is preferably that in any one of Modes 1 to 3, (MgF2 + BaF2) / (MgF2 + CaF2 + SrF2 + BaF2) is 0.25 to 1. Here, "(MgF2 + BaF2) / (MgF2 + CaF2 + SrF2 + BaF2)" means the value obtained by dividing the total amount of MgF2 and BaF2 by the total amount of MgF2, CaF2, SrF2, and BaF2.

[0017] For the halide glass of Mode 5, it is preferably that in any one of Modes 1 to 4, it contains, in mol%, YF3 + MgF2 + BaF2 20% to 80%. Here, "YF3 + MgF2 + BaF2" means the total amount of YF3, MgF2, and BaF2.

[0018] For the halide glass of Mode 6, it is preferably that in any one of Modes 1 to 5, AlF3 / (YF3 + MgF2 + BaF2) is 0.2 to 1. Here, "AlF3 / (YF3 + MgF2 + BaF2)" means the value obtained by dividing the content of AlF3 by the total amount of YF3, MgF2, and BaF2.

[0019] For the halide glass of Mode 7, it is preferably that in any one of Modes 1 to 6, the Abbe number (νd) is 85 to 110.

[0020] For the halide glass of Mode 8, it is preferably that in any one of Modes 1 to 7, the partial dispersion ratio (θg,F) is 0.515 to 0.54.

[0021] The optical element of Mode 9 is characterized by including the halide glass of any one of Modes 1 to 8.

[0022] Advantages of the Invention

[0023] According to the present invention, it is possible to provide a halide glass and an optical element having dispersion characteristics comparable to those of fluorite. Detailed Embodiments

[0024] The halide glass of the present invention is characterized by containing, in mol%, AlF3 of 15% to less than 29%, YF3 of 5% to 40%, and MgF2 + CaF2 + SrF2 + BaF2 of 26% to 80%. The reasons for defining the contents of the respective components as described above are shown below. It should be noted that in the description of the contents of the respective components, unless otherwise specified, % represents mol%.

[0025] AlF3 is an essential component for improving the stability of the glass. The content of AlF3 is preferably 15% to less than 29%, more preferably 16% to 28.9%, 16% to 28%, 17% to 27%, 18% to 26%, and particularly preferably 20% to 25%. If the content of AlF3 is too small, crystallization is likely to occur. If the content of AlF3 is too large, the partial dispersion ratio (θg,F) is likely to become low. Therefore, it is difficult to obtain dispersion characteristics comparable to those of fluorite. In addition, from the viewpoint of increasing the refractive index nd, the upper limit of the content of AlF3 can also be less than 20%, and particularly preferably 19% or less.

[0026] YF3 is an essential component for improving the stability of the glass. In addition, it is a component that particularly easily increases the partial dispersion ratio (θg,F). The content of YF3 is preferably 5% to 40%, 6% to 40%, 7% to 40%, 10% to 38%, 12% to 38%, 15% to 38%, 18% to 38%, 20% to 36%, and particularly preferably 25% to 36%. If the content of YF3 is too small, the partial dispersion ratio (θg,F) is likely to become low. If the content of YF3 is too large, crystallization is likely to occur.

[0027] AlF3 / YF3 is preferably 5 or less, 4.9 or less, 4.5 or less, 4 or less, 3.9 or less, 3.5 or less, 3 or less, 2.9 or less, 2.5 or less, 2 or less, and particularly preferably 1.9 or less. By satisfying the above values, it is easy to further increase the partial dispersion ratio (θg,F). The lower limit of AlF3 / YF3 is not particularly limited, and for example, it can be 0.43 or more, 0.45 or more, and particularly 0.5 or more.

[0028] MgF2, CaF2, SrF2, and BaF2 are components that can easily improve the stability of glass. The content of MgF2 + CaF2 + SrF2 + BaF2 is 26% to 80%, preferably 30% to 78%, 35% to 76%, 40% to 74%, 40% to 72%, 40% to 70%, 45% to 70%, 50% to 70%, and particularly preferably greater than 55% and 70% or less. If the content of MgF2 + CaF2 + SrF2 + BaF2 is too low, it is difficult to obtain the above effects. If the content of MgF2 + CaF2 + SrF2 + BaF2 is too high, the Abbe number (νd) tends to be too high. In addition, the partial dispersion ratio (θg,F) tends to be too low. It should be noted that the preferred contents of each component of MgF2, CaF2, SrF2, and BaF2 are as described below.

[0029] Among the above components, MgF2 is a component that can easily improve the stability of glass and can easily improve the partial dispersion ratio (θg,F). The content of MgF2 is preferably 0% to 24%, 1% to 24%, 5% to 24%, 8% to 24%, 10% to 24%, 11% to 24%, 11% to 22%, 11% to 20%. If the content of MgF2 is too high, it is prone to crystallization. However, from the perspective of improving the partial dispersion ratio (θg,F), the lower limit of the content of MgF2 can be 19% or more, 20% or more, and particularly, it can be greater than 20%.

[0030] CaF2 is a component that can easily improve the stability of glass. The content of CaF2 is preferably 0% to 33%, 1% to 33%, 5% to 33%, 8% to 33%, and particularly preferably 10% to 33%. If the content of CaF2 is too high, the Abbe number (νd) tends to be too high. In addition, the partial dispersion ratio (θg,F) is particularly prone to being too low.

[0031] SrF2 is a component that can easily improve the stability of glass. The content of SrF2 is preferably 0% to 23%, 0% to 20%, 0% to 15%, and particularly preferably 0% to 10%. If the content of SrF2 is too high, it is prone to crystallization. In addition, the partial dispersion ratio (θg,F) tends to become smaller. From the perspective of improving the partial dispersion ratio (θg,F), the upper limit of the content of SrF2 can be set to 9% or less, and particularly, it can be set to 7% or less.

[0032] Among the above components, BaF2 is a component that can easily improve the stability of glass, improve the partial dispersion ratio (θg,F), and easily reduce the Abbe number (νd). The content of BaF2 is preferably 0% to 20%, 1% to 20%, 3% to 20%, 5% to 20%, 72% to 20%, 8.5% to 20%, 10% to 20%, 11% to 18%, and particularly preferably 11% to 17%. If the content of BaF2 is too high, it is prone to crystallization.

[0033] Among the above components, especially by containing MgF2 and BaF2 as essential components, it is easy to increase the partial dispersion ratio (θg,F) and easy to decrease the Abbe number (νd). Therefore, the total amount of MgF2 + BaF2 (the total amount of MgF2 and BaF2) is preferably greater than 0% and 44% or less, 1% - 44%, 5% - 44%, 10% - 4%, 18% - 40%, 20% - 40%, and particularly preferably 22% - 38%. In addition, (MgF2 + BaF2) / (MgF2 + CaF2 + SrF2 + BaF2) is preferably 0.01 or more, 0.03 or more, 0.05 or more, 0.1 or more, 0.2 or more, 0.25 or more, 0.3 or more, and particularly preferably 0.5 or more. The upper limit of (MgF2 + BaF2) / (MgF2 + CaF2 + SrF2 + BaF2) is not particularly limited, and for example, it can be 1 or less, 0.99 or less, 0.95 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and particularly can be 0.5 or less.

[0034] From the viewpoint of increasing the partial dispersion ratio (θg,F) and decreasing the Abbe number (νd), the lower limit of MgF2 / (MgF2 + CaF2 + SrF2 + BaF2) is preferably 0.01 or more, 0.03 or more, 0.05 or more, 0.1 or more, and particularly preferably 0.15 or more. The upper limit of MgF2 / (MgF2 + CaF2 + SrF2 + BaF2) is not particularly limited, and for example, it can be 1 or less, 0.99 or less, 0.95 or less, 0.9 or less, and particularly 0.8 or less. Similarly, from the viewpoint of increasing the partial dispersion ratio (θg,F) and decreasing the Abbe number (νd), the lower limit of BaF2 / (MgF2 + CaF2 + SrF2 + BaF2) is preferably 0.01 or more, 0.03 or more, 0.05 or more, and particularly preferably 0.1 or more. The upper limit of BaF2 / (MgF2 + CaF2 + SrF2 + BaF2) is not particularly limited, and for example, it can be 1 or less, 0.99 or less, 0.95 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, and particularly 0.5 or less.

[0035] From the viewpoints of improving the stability of the glass, increasing the partial dispersion ratio, and decreasing the Abbe number (νd), the content of YF3 + MgF2 + BaF2 is preferably 20% - 80%, 20% - 75%, 25% - 75%, 25% - 70%, and particularly preferably 30% - 70%. If the content of YF3 + MgF2 + BaF2 is too small, it is difficult to obtain the above effects. If the content of YF3 + MgF2 + BaF2 is too large, crystallization is likely to occur.

[0036] In particular, from the viewpoint of improving the partial dispersion ratio (θg,F), AlF3 / (YF3 + MgF2 + BaF2) is preferably 1 or less, 0.9 or less, 0.89 or less, 0.8 or less, 0.7 or less, 0.6 or less, and particularly preferably 0.5 or less. On the other hand, from the viewpoint of suppressing the crystallization of the glass and stably forming the glass, AlF3 / (YF3 + MgF2 + BaF2) is preferably 0.18 or more, and particularly preferably 0.2 or more.

[0037] The halide glass of the present invention may also contain other fluoride components. For example, from the viewpoint of stabilizing vitrification and obtaining desired optical properties, NaF, ZrF4, HfF4, GaF3, InF3, and ZnF2 may be contained at 0% to less than 10%, less than 5%, particularly 0% to less than 3%, respectively, or NaF, ZrF4, HfF4, GaF3, InF3, and ZnF2 may be contained in a total amount of 0% to 15%, 0% to 10%, 0% to 5%, particularly 0% to 3%. In particular, from the viewpoint of stabilizing vitrification, the total amount of ZrF4 and HfF4 is preferably 0% to less than 5%, and particularly preferably 0% to less than 3%.

[0038] The halide glass of the present invention is a so-called fluoride glass mainly composed of fluoride. However, in the halide glass of the present invention, in addition to fluoride, any of the following components may be contained.

[0039] The halide glass of the present invention may also contain chloride components such as AlCl3, YCl3, LaCl3, GdCl3, YbCl3, MgCl2, CaCl2, SrCl2, and BaCl2. By containing the chloride components, the stability of the glass is easily improved. From the viewpoint of reliably enjoying the effects of the present invention, the content of the above chloride components is preferably 15% or less, 10% or less, and particularly preferably 5% or less in total. The lower limit of the content of the chloride components may be, for example, 0% or more, 0.1% or more, and particularly may be 0.5% or more.

[0040] The halide glass of the present invention may contain phosphate components such as Al(PO3)3, Mg(PO3)2, Ca(PO3)2, Sr(PO3)2, Ba(PO3)2, P2O5, and KPF6. By containing the phosphate components, the stability of the glass can be improved. From the viewpoint of reliably enjoying the effects of the present invention, the content of the above phosphate components is preferably 15% or less, 10% or less, and particularly preferably 5% or less in total. The lower limit of the content of the phosphate components may be, for example, 0% or more, 0.1% or more, and particularly may be 0.5% or more.

[0041] From the viewpoint of reducing the environmental impact, the halide glass of the present invention preferably substantially does not contain U, Th, Be, or Pb. For example, it preferably substantially does not contain UF4, ThF4, BeF2, or PbF2. Here, "substantially does not contain" means that it is not intentionally contained as a raw material, and does not exclude the incorporation of unavoidable impurities. Objectively, it means that the content is less than 0.1%, particularly less than 0.01%.

[0042] The halide glass of the present invention may contain rare earth ions as luminescent components. For example, as rare earth ions, 0% to 5% of Tm ions, Er ions, Yb ions, or Ho ions may be contained respectively. However, if the content of rare earth ions is too high, there is a tendency for vitrification to become unstable. Therefore, from the viewpoint of stabilizing vitrification, the upper limit of the content of Tm ions, Er ions, Yb ions, or Ho ions is preferably 3% or less, 1% or less, and particularly preferably substantially does not contain.

[0043] The halide glass of the present invention can have dispersion characteristics comparable to those of fluorite by satisfying the above composition. For example, the Abbe number (νd) of the halide glass of the present invention is preferably 85 to 110, and the partial dispersion ratio (θg,F) is preferably 0.515 to 0.54.

[0044] The Abbe number (νd) is preferably 85 to 110, 90 to 100, 90 to 99.4, 90 to 99.1, 91 to 99, 91 to 98, and particularly preferably 92 to 98. By having the above Abbe number (νd), the halide glass of the present invention can be suitably used as a substitute material for fluorite.

[0045] The partial dispersion ratio (θg,F) is preferably 0.515 to 0.54, 0.516 to 0.5399, 0.517 to 0.5398, 0.517 to 0.5397, and particularly preferably 0.517 to 0.5395. By having the above partial dispersion ratio (θg,F), the halide glass of the present invention exhibits abnormal partial dispersion comparable to that of fluorite. Therefore, it can be suitably used as a substitute material for fluorite.

[0046] The halide glass of the present invention preferably has a refractive index (nd) of 1.4 to 1.5, and particularly preferably 1.41 to 1.46. By having the above refractive index, the halide glass of the present invention can be suitably used as a substitute material for fluorite whose refractive index is also comparable to that of fluorite.

[0047] The halide glass of the present invention can be suitably used as an optical element. In other words, the optical element of the present invention is characterized by containing the above halide glass of the present invention. As optical elements, for example, optical lenses, prisms, filters, diffraction gratings, optical fibers, etc. can be cited, and particularly preferably optical lenses. As optical lenses, low-dispersion lenses and special low-dispersion lenses are preferred.

[0048] The halide glass of the present invention can be produced, for example, as follows.

[0049] First, raw materials are weighed in such a way as to achieve a desired composition to obtain a raw material batch. Next, the raw material batch is put into a crucible. As the crucible, a platinum crucible, a gold crucible, a glassy carbon crucible, etc. can be used.

[0050] Next, the raw material batch is melted at about 900°C to 1200°C for several hours. Then, the melt is quenched and annealed near the glass transition temperature, thereby obtaining the halide glass.

[0051] Examples

[0052] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0053] Tables 1 and 2 show Examples 1 to 12 and Comparative Example 1 of the present invention.

[0054] [Table 1]

[0055]

[0056] [Table 2]

[0057]

[0058] The specimens are produced according to the following steps. First, raw materials are weighed in such a way as to achieve the compositions described in Tables 1 and 2 to obtain a raw material batch. Next, the raw material batch is introduced into a crucible and melted at 900°C to 1200°C for several hours. After melting, the melt is quenched and annealed near the glass transition temperature, thereby obtaining the specimens. The refractive index of the obtained specimens is measured, and the Abbe number (νd) and the partial dispersion ratio (θg,F) are calculated. The results of the refractive index (nd), the Abbe number (νd), and the partial dispersion ratio (θg,F) are shown in Tables 1 and 2.

[0059] The refractive index is measured using a known V-block method. The measurement is performed using a Kalneur precision refractometer (manufactured by Shimadzu Corporation, KPR-2000).

[0060] The Abbe number (νd) and the partial dispersion ratio (θg,F) are calculated from the measured refractive indices nd (587.56 nm), nC (656.27 nm), nF (486.07 nm), and ng (435.83 nm) using the following formulas.

[0061] νd = (nd - 1) / (nF - nC)

[0062] θg,F = (ng - nF) / (nF - nC)

[0063] As shown in Tables 1 and 2, the refractive index (nd) of Examples 1 to 12 was 1.41638 or more, the Abbe number (νd) was 99.1 or less, and the partial dispersion ratio (θg,F) was 0.5174 or more. On the other hand, the partial dispersion ratio (θg,F) of Comparative Example 1 was as low as 0.5142.

[0064] Industrial Applicability

[0065] The halide glass of the present invention can be suitably used as optical elements such as lenses, prisms, filters, diffraction gratings, and optical fibers. In particular, it can be suitably used as a low-dispersion lens and a special low-dispersion lens.

Claims

1. A halide glass, characterized in that it contains, in mol%, AlF3 15% to less than 29%, YF3 5% to 40%, and MgF2 + CaF2 + SrF2 + BaF2 26% to 80%.

2. The halide glass according to claim 1, wherein AlF3 / YF3 is 5 or less.

3. The halide glass according to claim 1 or 2, wherein it contains, in mol%, MgF2 11% to 24%, CaF2 8% to 33%, SrF2 0% to 23%, and BaF2 7% to 20%.

4. The halide glass according to claim 1 or 2, wherein (MgF2 + BaF2) / (MgF2 + CaF2 + SrF2 + BaF2) is 0.25 to 1.

5. The halide glass according to claim 1 or 2, wherein it contains, in mol%, YF3 + MgF2 + BaF2 20% to 80%.

6. The halide glass according to claim 1 or 2, wherein AlF3 / (YF3 + MgF2 + BaF2) is 0.2 to 1.

7. The halide glass according to claim 1 or 2, wherein the Abbe number (νd) is 85 to 110.

8. The halide glass according to claim 1 or 2, wherein the partial dispersion ratio (θg,F) is 0.515 to 0.

54.

9. An optical element comprising the halide glass according to claim 1 or 2.

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