Optical glass and optical element

Abstract

Provided is a phosphoric acid-based glass having a low coefficient of thermal expansion. In the optical glass, in terms of mass, the content of B2O3 is from 3.00% to 70.00% (inclusive), the content of P2O5 is from 47.00% to 80.00% (inclusive), the content of Al2O3 is 13.00% or less, the content of Li2O is 0.01% or more, the content of Na2O is 5.00% or less, the content of CaO is 18.00% or less, the content of ZnO is 23.00% or less, the refractive index nd of the optical glass is 1.70000 or less, the Abbe number vd is 60.00 or more, and the optical glass has excellent optical properties. And the average linear expansion coefficient [alpha] at 100-300 DEG C is 130 * 10-7 / K or less.

Description

Technical Field

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

[0002] Phosphate-based glass is generally an optical glass having low dispersion, and has been used as a material for various optical elements (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-269980 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] One of the desirable properties of optical glass is a low thermal expansion coefficient. This is because, for example, optical glass with a low thermal expansion coefficient can suppress the occurrence of breakage and cracks in the glass during press molding.

[0008] An object of one embodiment of the present invention is to provide phosphate-based glass having a low thermal expansion coefficient.

[0009] Optical glass is also expected to have excellent weather resistance. One reason for this is that, when pressure is applied to glass with a denatured surface, it may become noticeably hazy or have scratches formed on the denatured portion.

[0010] Another aspect of the present invention aims to provide a phosphate-based glass having a low thermal expansion coefficient and excellent weather resistance.

[0011] Solutions to the problem

[0012] The present inventors have conducted intensive studies and have newly discovered that phosphate-based glass having the following glass composition can exhibit a low thermal expansion coefficient.

[0013] One embodiment of the present invention is as follows.

[0014] [A1] An optical glass (hereinafter referred to as "optical glass" or simply "glass"), wherein:

[0015] Based on quality standards,

[0016] The B2O3 content is 3.00% or more and 70.00% or less,

[0017] P2O5 content is 47.00% or more and 80.00% or less,

[0018] Al2O3 content is less than 13.00%,

[0019] Li2O content is above 0.01%,

[0020] Na2O content is less than 5.00%,

[0021] CaO content is less than 18.00%,

[0022] The ZnO content is less than 23.00%,

[0023] The total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is 66.00% or more and 84.00% or less,

[0024] The total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 26.00% or less. Specifically, when the total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 15.00% or more and 26.00% or less, the total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is 69.00% or more and 84.00% or less.

[0025] The total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is less than 15.00%,

[0026] The mass ratio of P2O5 content to B2O3 content (P2O5 / B2O3) is 18.00 or less,

[0027] The mass ratio of the Na2O content to the total content of Li2O, Na2O and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.50 or less,

[0028] The total content of MgO and CaO (MgO+CaO) is 2.00% or more,

[0029] The mass ratio of the total content of Li2O and BaO to the content of B2O3 ((Li2O+BaO) / B2O3) is 0.59 or less,

[0030] The mass ratio of the total content of Al2O3 and BaO to the content of Li2O ((Al2O3+BaO) / Li2O) is 2.77 or less,

[0031] The mass ratio of the total content of MgO and CaO to the total content of Li2O, Na2O and K2O ((MgO+CaO) / (Li2O+Na2O+K2O)) is 6.10 or less,

[0032] The mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of P2O5, B2O3 and SiO2 ((MgO+CaO+SrO+BaO+ZnO) / (P2O5+B2O3+SiO2)) is 0.36 or less,

[0033] The optical glass has a refractive index nd of 1.70000 or less, an Abbe number νd of 60.00 or more, and an average linear expansion coefficient α at 100°C to 300°C of 130×10 -7 / K or less.

[0034] [A2] The optical glass according to [A1], wherein

[0035] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 7.00% or less.

[0036] [A3] The optical glass according to [A1] or [A2], wherein:

[0037] The Nb2O5 content is 5.00% or less.

[0038] [A4] The optical glass according to any one of [A1] to [A3], wherein

[0039] The total content of MgO, CaO, SrO, and BaO (MgO+CaO+SrO+BaO) is 4.90% or more and 26.00% or less.

[0040] [A5] The optical glass according to any one of [A1] to [A4], wherein

[0041] The mass ratio of the Na2O content to the total content of Li2O, Na2O, and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.19 or less.

[0042] [A6] The optical glass according to any one of [A1] to [A5], wherein

[0043] The total content of ZnO and BaO (ZnO+BaO) is 20.50% or less.

[0044] [A7] The optical glass according to any one of [A1] to [A6], wherein

[0045] The SiO2 content is less than 5.00%.

[0046] [A8] The optical glass according to any one of [A1] to [A7], wherein

[0047] CaO content is less than 9.00%,

[0048] Alternatively, the CaO content is 9.00% or more and 18.00% or less, and the total content of SrO and BaO (SrO+BaO) is less than 3.00%.

[0049] [A9] The optical glass according to any one of [A1] to [A8], wherein

[0050] The total content of SrO and BaO (SrO+BaO) is 13.00% or less.

[0051] [A10] The optical glass according to any one of [A1] to [A9], wherein

[0052] The total content of SrO, BaO and K2O (SrO+BaO+K2O) is 13.00% or less.

[0053] [A11] The optical glass according to any one of [A1] to [A10], wherein

[0054] The mass ratio of the total content of SrO and BaO to the content of Li2O ((SrO+BaO) / Li2O) is 5.00 or less.

[0055] [A12] The optical glass according to any one of [A1] to [A11], wherein

[0056] The P2O5 content is 47.00% or more and less than 58.00%,

[0057] Alternatively, the P2O5 content is greater than 58.00% and less than 80.00% and the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li2O, Na2O and K2O ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+K2O)) is less than 6.00.

[0058] [A13] The optical glass according to any one of [A1] to [A12], having a specific gravity of 3.00 g / cc or less.

[0059] [A14] The optical glass according to any one of [A1] to [A13], wherein the external transmittance at a wavelength of 400 nm to 700 nm is 60% or more when converted to a thickness of 10.0 mm.

[0060] [A15] The optical glass according to any one of [A1] to [A14], wherein

[0061] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is less than 7.00%, and the content of Nb2O5 is less than 5.00%.

[0062] The total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 4.90% or more and 26.00% or less,

[0063] The mass ratio of the Na2O content to the total content of Li2O, Na2O and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.19 or less,

[0064] The total content of ZnO and BaO (ZnO+BaO) is less than 20.50%,

[0065] SiO2 content is less than 5.00%,

[0066] The CaO content is less than 9.00% and the total content of SrO and BaO (SrO+BaO) is 13.00% or less, or the CaO content is 9.00% or more and 18.00% or less and the total content of SrO and BaO (SrO+BaO) is less than 3.00%,

[0067] The total content of SrO, BaO and K2O (SrO+BaO+K2O) is less than 13.00%,

[0068] The mass ratio of the total content of SrO and BaO to the content of Li2O ((SrO+BaO) / Li2O) is 5.00 or less,

[0069] The P2O5 content is 47.00% or more and less than 58.00%, or the P2O5 content is 58.00% or more and 80.00% or less and the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li2O, Na2O and KO ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+KO)) is less than 6.00,

[0070] The optical glass has a specific gravity of 3.00 g / cc or less and an external transmittance of 60% or more at a wavelength of 400 nm to 700 nm based on a thickness of 10.0 mm.

[0071] [A16] An optical element made of the optical glass described in any one of [A1] to [A15].

[0072] Hereinafter, an optical glass satisfying at least the above-mentioned [A1] will be referred to as "glass A".

[0073] Furthermore, the present inventors have conducted intensive studies and have newly discovered that phosphate glass having the following glass composition can exhibit a low thermal expansion coefficient and excellent weather resistance.

[0074] One embodiment of the present invention is as follows.

[0075] [B1] An optical glass, wherein:

[0076] Based on quality standards,

[0077] The SiO2 content is 0.00% or more and 5.00% or less,

[0078] The B2O3 content is 0.00% or more and 20.00% or less,

[0079] The P2O5 content is 60.00% or more, and when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more,

[0080] The Al2O3 content is 1.00% or more and 30.00% or less,

[0081] The K2O content is 0.00% or more and 5.00% or less,

[0082] The MgO content is 0.00% or more and 10.00% or less,

[0083] The CaO content is 0.00% or more and 15.00% or less,

[0084] The SrO content is 0.00% or more and 5.00% or less,

[0085] The BaO content is 0.00% or more and 5.00% or less,

[0086] The ZnO content is 0.00% or more and 5.00% or less,

[0087] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is more than 71.00%,

[0088] The total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is 1.40% or more and 6.00% or less,

[0089] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00% or more and 4.00% or less,

[0090] The optical glass has a refractive index nd of 1.49000 or more, an Abbe number νd of 65.00 or more, and an average linear expansion coefficient α (-30 / 70) of 90×10 -7 / K or less, and the difference in fogging amount before and after the weathering test is D H It is 0.0% or more and 5.0% or less.

[0091] [B2] The optical glass according to [B1], wherein

[0092] The P2O5 content is 60.00% or more and 80.00% or less, and when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more and 80.00% or less,

[0093] Furthermore, the Al2O3 content is 1.00% or more and 14.00% or less.

[0094] [B3] The optical glass according to [B1], wherein

[0095] Based on quality standards,

[0096] The SiO2 content is 0.00% or more and 3.00% or less,

[0097] The B2O3 content is 0.00% or more and 12.50% or less, wherein the B2O3 content is 4.75% or more and 12.50% or less when the P2O5 content is 77.00% or more and the Al2O3 content is 14.00% or more and 30.00% or less,

[0098] The Li2O content is 1.00% or more and 10.00% or less,

[0099] The ZnO content is 0.00% or more and 3.50% or less,

[0100] The CuO content is 0.00% or more and less than 0.50%,

[0101] The B2O3 content is 3.00% or more and 20.00% or less, or the B2O3 content is 0.00% or more and less than 3.00% and the total content of MgO and CaO is 10.10% or more,

[0102] The P2O5 content is 60.00% or more and less than 77.0%, or the P2O5 content is 77.00% or more and the Al2O3 content is 11.00% or more and 30.00% or less,

[0103] Furthermore, the CaO content is 0.00% or more and less than 0.50%, or the CaO content is 0.50% or more and 15.00% or less and the Al2O3 content is 1.00% or more and less than 14.00%.

[0104] [B4] The optical glass according to [B3], wherein

[0105] The total content of MgO and CaO (MgO+CaO) exceeds 3.00%,

[0106] or,

[0107] The total content of MgO and CaO (MgO+CaO) is 0.00% or more and 3.00% or less, and the Al2O3 content is 7.00% or more and 30.00% or less.

[0108] [B5] The optical glass according to [B3] or [B4], wherein:

[0109] The SiO2 content is 0.00% or more and 3.00% or less.

[0110] [B6] The optical glass according to any one of [B3] to [B5], wherein

[0111] The Al2O3 content is 4.00% or more and 30.00% or less.

[0112] [B7] The optical glass according to any one of [B3] to [B6], wherein

[0113] The Na2O content is 0.00% or more and 5.00% or less.

[0114] [B8] The optical glass according to any one of [B3] to [B7], wherein

[0115] The K2O content is 0.00% or more and 2.50% or less.

[0116] [B9] The optical glass according to any one of [B3] to [B8], wherein

[0117] The MgO content is 0.00% or more and 7.00% or less.

[0118] [B10] The optical glass according to any one of [B3] to [B9], wherein

[0119] The ZnO content is 0.00% or more and 3.10% or less.

[0120] [B11] The optical glass according to any one of [B3] to [B10], wherein

[0121] It contains virtually no PbO.

[0122] [B12] The optical glass according to any one of [B3] to [B11], wherein

[0123] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is more than 75.00%.

[0124] [B13] The optical glass according to any one of [B3] to [B12], wherein

[0125] The mass ratio of the Al2O3 content to the P2O5 content (Al2O3 / P2O5) is 0.20 or less.

[0126] [B14] The optical glass according to any one of [B3] to [B13], wherein

[0127] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00%.

[0128] or,

[0129] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) exceeds 0.000% and is 4.00% or less, and the total content of P2O5 and B2O3 (P2O5+B2O3) exceeds 80.00%.

[0130] [B15] The optical glass according to any one of [B3] to [B14], wherein

[0131] The Sb2O3 content is 0.01 mass % or more as an added ratio.

[0132] [B16] The optical glass according to any one of [B3] to [B15], wherein

[0133] The Al2O3 content is 14.00% or more and the mass ratio of the Li2O content to the Al2O3 content (Li2O / Al2O3) is 0.13 or less.

[0134] [B17] An optical element made of the optical glass described in any one of [B1] to [B16].

[0135] Hereinafter, optical glass that satisfies at least [B1] is referred to as "Glass B." Optical glass that satisfies Glass B is also referred to as "optical glass" or simply "glass." Optical glass that satisfies at least [B1] and [B2] is referred to as "Glass B-1." Optical glass that satisfies at least [B1] and [B3] is referred to as "Glass B-2."

[0136] In addition, one embodiment of the present invention is as follows: An optical glass satisfying at least the following [1] is referred to as "Glass B-1".

[0137] [1] An optical glass, wherein:

[0138] Based on quality standards,

[0139] The SiO2 content is 0.00% or more and 5.00% or less,

[0140] The B2O3 content is 0.00% or more and 20.00% or less,

[0141] The P2O5 content is 60.00% or more and 80.00% or less, and when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more and 80.00% or less,

[0142] The Al2O3 content is 1.00% or more and 14.00% or less,

[0143] The K2O content is 0.00% or more and 5.00% or less,

[0144] The MgO content is 0.00% or more and 10.00% or less,

[0145] The CaO content is 0.00% or more and 15.00% or less,

[0146] The SrO content is 0.00% or more and 5.00% or less,

[0147] The BaO content is 0.00% or more and 5.00% or less,

[0148] The ZnO content is 0.00% or more and 5.00% or less,

[0149] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is more than 71.00%,

[0150] The total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is 1.40% or more and 6.00% or less,

[0151] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00% or more and 4.00% or less,

[0152] The optical glass has a refractive index nd of 1.49000 or more, an Abbe number νd of 65.00 or more, and an average linear expansion coefficient α (-30 / 70) of 90×10 -7 / K or less, and the difference in fogging amount before and after the weathering test is D H It is 0.0% or more and 5.0% or less.

[0153] [2] The optical glass according to [1], wherein:

[0154] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is 71.00% or more and less than 96.00%,

[0155] or,

[0156] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is greater than 96.00% and the total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is greater than 2.10% and less than 6.00%.

[0157] [3] The optical glass according to [1] or [2], wherein:

[0158] The total content of MgO and CaO (MgO+CaO) exceeds 0.00%,

[0159] or,

[0160] The total content of MgO and CaO (MgO+CaO) is 0.00% and the Li2O content is 3.10% or more.

[0161] [4] The optical glass according to any one of [1] to [3], wherein

[0162] The total content of MgO and CaO (MgO+CaO) exceeds 3.00%,

[0163] or,

[0164] The total content of MgO and CaO (MgO+CaO) is 0.00% or more and 3.00% or less, and the Al2O3 content is 7.00% or more and 14.00% or less.

[0165] [5] The optical glass according to any one of [1] to [4], wherein

[0166] The B2O3 content is 3.00% or more and 20.00% or less,

[0167] or,

[0168] The B2O3 content is 0.00% or more and less than 3.00% and the total content of MgO and CaO is 10.10% or more.

[0169] [6] The optical glass according to any one of [1] to [5], wherein

[0170] The P2O5 content is 60.00% or more and less than 77.0%,

[0171] or,

[0172] The P2O5 content is 77.00% or more and 80.00% or less and the Al2O3 content is 11.00% or more and 14.00% or less.

[0173] [7] The optical glass according to any one of [1] to [6], wherein

[0174] The SiO2 content is 0.00% or more and 3.00% or less.

[0175] [8] The optical glass according to any one of [1], wherein

[0176] The Al2O3 content is 4.00% or more and 14.00% or less.

[0177] [9] The optical glass according to any one of [1] to [8], wherein

[0178] The Na2O content is 0.00% or more and 3.00% or less.

[0179]

[10] The optical glass according to any one of [1] to [9], wherein

[0180] The K2O content is 0.00% or more and 2.50% or less.

[0181]

[11] The optical glass according to any one of [1] to

[10] , wherein

[0182] The MgO content is 0.00% or more and 7.00% or less.

[0183]

[12] The optical glass according to any one of [1] to

[11] , wherein

[0184] The ZnO content is 0.00% or more and 3.10% or less.

[0185]

[13] The optical glass according to any one of [1] to

[12] , wherein

[0186] It contains virtually no PbO.

[0187]

[14] The optical glass according to any one of [1] to

[13] , wherein

[0188] The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is more than 75.00%.

[0189]

[15] The optical glass according to any one of [1] to

[14] , wherein

[0190] The mass ratio of the Al2O3 content to the P2O5 content (Al2O3 / P2O5) is 0.20 or less.

[0191]

[16] The optical glass according to any one of [1] to

[15] , wherein

[0192] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00%.

[0193] or,

[0194] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) exceeds 0.000% and is 4.00% or less, and the total content of P2O5 and B2O3 (P2O5+B2O3) exceeds 80.00%.

[0195]

[17] An optical element made of the optical glass described in any one of [1] to

[16] .

[0196] Effects of the Invention

[0197] According to one embodiment of the present invention, there can be provided optical glass that is phosphate-based glass having a low thermal expansion coefficient, and an optical element made of the optical glass.

[0198] According to one embodiment of the present invention, there can be provided an optical glass that is a phosphate-based glass having a low thermal expansion coefficient and excellent weather resistance, and an optical element made of the optical glass. DETAILED DESCRIPTION

[0199] [Optical glass]

[0200] Unless otherwise specified, the following description applies to both optical glasses that conform to Glass A and optical glasses that conform to Glass B. Unless otherwise specified, the optical glasses described below may include both optical glasses that conform to Glass A and optical glasses that conform to Glass B.

[0201] <Glass Composition>

[0202] In the present invention and this specification, glass composition is expressed as an oxide-based glass composition. Here, "oxide-based glass composition" refers to the glass composition calculated based on the total amount of substances present as oxides in the glass after all glass raw materials decompose during melting. Unless otherwise specified, glass composition is expressed on a mass basis (mass %, mass ratio).

[0203] The glass composition of the present invention and this specification can be determined by methods such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed on each element separately using ICP-AES. The analyzed value is then converted to represent the oxide. The analyzed value based on ICP-AES may sometimes contain a measurement error of, for example, approximately ±5% of the analyzed value. Therefore, the value represented by the oxide converted from the analyzed value may also contain an error of approximately ±5%.

[0204] In the present invention and this specification, the phrases "substantially free of," "not containing," "not introduced," or "content of a constituent component is 0.00%" with respect to a certain component mean that the content of the component is below the impurity level. Below the impurity level means, for example, less than 0.01% by mass.

[0205] (Glass A)

[0206] Hereinafter, the glass composition of Glass A will be described in more detail.

[0207] B2O3 is a glass structure forming component. From the perspective of maintaining glass stability, the B2O3 content is 3.00% or more, preferably 4.00% or more, and more preferably 5.00% or more, 6.00% or more, 7.00% or more, 8.00% or more, and 9.00% or more in this order.

[0208] On the other hand, from the perspective of low dispersion of glass, the B2O3 content is less than 70.00%, preferably less than 60.00%, and more preferably less than 50.00%, less than 40.00%, less than 30.00%, less than 20.00%, less than 18.00%, less than 16.00%, less than 15.00%, less than 14.00%, and less than 13.00%.

[0209] Glass A is a phosphate glass and therefore contains P₂O₅. P₂O₅ is also a glass structure-forming component. To maintain glass stability, the P₂O₅ content is 47.00% or greater, preferably 50.00% or greater, with 52.00% or greater, 54.00% or greater, 56.00% or greater, 57.00% or greater, 58.00% or greater, 59.00% or greater, and 60.00% or greater being more preferred, in that order.

[0210] On the other hand, from the viewpoint of suppressing the increase in the glass transition temperature Tg, the P2O5 content is 80.00% or less, preferably 75.00% or less, and more preferably 70.00% or less, 69.00% or less, 68.00% or less, 67.00% or less, 66.00% or less, 65.00% or less, 64.00% or less, and 63.00% or less in this order.

[0211] In one embodiment, the P2O5 content may be less than 58.00%, and in another embodiment, it may be greater than 58.00%.

[0212] From the perspective of suppressing the reduction in the refractive index of the glass, the mass ratio of the P2O5 content to the B2O3 content (P2O5 / B2O3) is 18.00 or less, preferably 16.00 or less, and more preferably 14.00 or less, 12.00 or less, 11.00 or less, 10.00 or less, 9.00 or less, and 8.00 or less. From the perspective of achieving low dispersion in the glass, the mass ratio (P2O5 / B2O3) is preferably greater than 0.00, and more preferably 1.00 or more, 2.00 or more, 3.00 or more, 4.00 or more, and 5.00 or more.

[0213] Al2O3 is a component that can improve the stability of glass. The Al2O3 content can be, for example, 0.00%, 0.00% or more, more than 0.00%, 1.00% or more, 2.00% or more, 3.00% or more, or 4.00% or more.

[0214] However, it should be noted that the introduction of excessive Al2O3 tends to reduce the stability of the glass. Therefore, from the perspective of maintaining the stability of the glass, the Al2O3 content is 13.00% or less, preferably 12.00% or less, and more preferably 11.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, and 6.00% or less in this order.

[0215] SiO2 is also a component that can improve the stability of glass. The SiO2 content can be, for example, 0.00%, 0.00% or more, more than 0.00%, or 0.10% or more.

[0216] The SiO2 content may be, for example, 15.00% or less or 10.00% or less. From the perspective of suppressing the formation of striae, the SiO2 content is preferably 5.00% or less, and more preferably 4.50% or less, 4.00% or less, 3.50% or less, 3.00% or less, 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, and 0.80% or less in this order.

[0217] From the perspective of maintaining the stability of the glass, the total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is 66.00% or more, preferably 68.00% or more, and more preferably 70.00% or more and 72.00% or more in that order.

[0218] Among them, when the total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is more than 15.00%, from the perspective of maintaining the stability of the glass and reducing the thermal expansion coefficient, the total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is more than 69.00%.

[0219] On the other hand, from the perspective of suppressing the low refractive index of the glass, the total content (P2O5+B2O3+SiO2) is less than 84.00%, preferably less than 83.00%, and more preferably less than 82.00%, less than 81.00%, less than 80.00%, less than 79.00%, less than 78.00%, less than 77.00%, and less than 76.00%.

[0220] From the viewpoint of suppressing the low refractive index of the glass, the total content of Li2O, Na2O and K2O (Li2O + Na2O + K2O) is 15.00% or less, preferably 14.00% or less, and more preferably 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, and 5.00% or less in this order.

[0221] The total content (Li2O+Na2O+K2O) may be, for example, 0.01% or more, or 0.10% or more, 1.00% or more, 2.00% or more, or 3.00% or more.

[0222] Li2O contributes to lowering the thermal expansion coefficient of glass, reducing dispersion, and increasing the refractive index. It also lowers the glass transition temperature (Tg). The Li2O content is 0.01% or higher, preferably 0.10% or higher, and more preferably 0.30% or higher, 0.50% or higher, 0.80% or higher, 1.00% or higher, 1.30% or higher, 1.50% or higher, 1.80% or higher, 2.00% or higher, 2.30% or higher, 2.80% or higher, and 3.00% or higher, in this order.

[0223] From the viewpoint of maintaining the stability of the glass, the Li2O content is preferably 10.00% or less, and more preferably 9.50% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.00% or less, 6.50% or less, 6.00% or less, 5.50% or less, and 5.00% or less in this order.

[0224] Na2O is a component that contributes to lowering the thermal expansion coefficient of glass and reducing dispersion. The Na2O content may be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.01% or more, or 0.10% or more.

[0225] From the viewpoint of maintaining the stability of the glass, the Na2O content is 5.00% or less, preferably 4.80% or less, and more preferably 4.50% or less, 4.30% or less, 4.00% or less, 3.80% or less, 3.50% or less, 3.30% or less, 3.00% or less, 2.80% or less, 2.50% or less, 2.20% or less, 2.00% or less, 1.80% or less, 1.50% or less, 1.30% or less, 1.00% or less, 0.80% or less, and 0.50% or less in this order.

[0226] The K2O content may be, for example, 0.00% or more. From the viewpoint of maintaining the stability of the glass, it is preferably more than 0.00%, and more preferably 0.01% or more, and 0.10% or more in this order.

[0227] From the viewpoint of further reducing the thermal expansion coefficient of the glass, the K2O content is preferably 15.00% or less, and more preferably 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.50% or less, 7.00% or less, 6.50% or less, 6.00% or less, 5.50% or less, 5.00% or less, 4.50% or less, 4.00% or less, 3.50% or less, 3.00% or less, 2.50% or less, 2.00% or less, 1.50% or less, and 1.00% or less in this order.

[0228] The mass ratio of the Na2O content to the total content of Li2O, Na2O and K2O (Na2O / (Li2O+Na2O+K2O)) can be 0.00, 0.00 or more, more than 0.00, 0.01 or more, 0.50 or more, or 0.10 or more.

[0229] From the viewpoint of suppressing the low refractive index of the glass, the mass ratio (Na2O / (Li2O+Na2O+K2O)) is 0.50 or less, preferably 0.40 or less, and more preferably 0.30 or less, 0.25 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, and 0.15 or less in this order.

[0230] From the perspective of suppressing high dispersion of glass and increasing the thermal expansion coefficient, the total content of MgO and CaO (MgO + CaO) is 2.00% or more, preferably 4.00% or more, and more preferably 6.00% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, and 14.00% or more. Furthermore, the total content (MgO + CaO) can be, for example, 24.00% or less, 23.00% or less, 22.00% or less, 21.00% or less, 20.00% or less, 19.00% or less, or 18.00% or less.

[0231] From the viewpoint of suppressing high dispersion of glass, the total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 26.00% or less, preferably 24.00% or less, and more preferably 22.00% or less, 21.00% or less, 20.00% or less, 19.00% or less and 18.00% or less in this order.

[0232] On the other hand, from the viewpoint of suppressing the low refractive index of the glass, the total content (MgO+CaO+SrO+BaO) is preferably 4.90% or more, more preferably 5.00% or more, and more preferably 5.50% or more, 6.00% or more, 7.00% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, and 14.00% or more in this order.

[0233] In one embodiment, the total content (MgO+CaO+SrO+BaO) may be less than 15.00%, and in another embodiment, may be 15.00% or more.

[0234] From the perspective of suppressing an increase in the coefficient of thermal expansion of the glass, the total content of SrO and BaO (SrO + BaO) is preferably 13.00% or less, and more preferably 12.00% or less, 11.00% or less, 10.00% or less, 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, less than 3.00%, 2.00% or less, 1.50% or less, and 1.00% or less. The total content (SrO + BaO) can be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.01% or more, or 0.10% or more.

[0235] CaO is a component that contributes to lowering the thermal expansion coefficient of glass and reducing dispersion. The CaO content can be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, 8.00% or more, or 9.00% or more.

[0236] From the viewpoint of suppressing high dispersion of glass, the CaO content is 18.00% or less, preferably 16.00% or less, and more preferably 15.00% or less, 14.50% or less, 14.00% or less, 13.50% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, less than 9.00%, and 8.00% or less.

[0237] In glass A, in one embodiment, the CaO content is less than 9.00%, and in another embodiment, the CaO content is 9.00% or greater. When the CaO content is 9.00% or greater, from the perspective of achieving low dispersion in the glass, the total content (SrO + BaO) is preferably less than 3.00%, with the content being more preferably 2.80% or less, 2.50% or less, 2.20% or less, 2.00% or less, 1.80% or less, 1.50% or less, 1.30% or less, 1.10% or less, and 1.00% or less being the most preferred. In this case, the total content (SrO + BaO) can be, for example, 0.00%, 0.00% or greater, more than 0.00%, 0.01% or greater, or 0.10% or greater.

[0238] MgO is also a component that contributes to lowering the thermal expansion coefficient of glass and reducing dispersion. The MgO content can be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, or 1.00% or more. Furthermore, the MgO content can be, for example, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, or 4.00% or less.

[0239] SrO and BaO are components that contribute to lowering the thermal expansion coefficient of glass.

[0240] The SrO content may be, for example, 0.00% or more. From the viewpoint of maintaining the stability of the glass, it is preferably more than 0.00%, and more preferably 0.10% or more and 1.00% or more in this order.

[0241] From the viewpoint of suppressing an increase in the thermal expansion coefficient of the glass, the SrO content is preferably 16.00% or less, and more preferably 14.00% or less, 12.00% or less, 10.00% or less, 8.00% or less, 6.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, and 1.00% or less.

[0242] The BaO content may be, for example, 0.00% or more. From the viewpoint of maintaining the stability of the glass, it is preferably more than 0.00%, more preferably 0.10% or more, and more preferably 1.00% or more in this order.

[0243] From the viewpoint of suppressing an increase in the thermal expansion coefficient of glass, the BaO content is preferably 10.00% or less, more preferably 8.00% or less, 6.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, and 1.00% or less in this order.

[0244] From the perspective of achieving low dispersion of glass and reducing the coefficient of thermal expansion, the mass ratio of the total content of Li₂O and BaO to the content of B₂O₃ ((Li₂O + BaO) / B₂O₃) is 0.59 or less, preferably 0.57 or less, and more preferably 0.55 or less, 0.53 or less, 0.51 or less, 0.49 or less, 0.47 or less, 0.45 or less, 0.43 or less, 0.41 or less, 0.39 or less, and 0.37 or less, in this order. The mass ratio ((Li₂O + BaO) / B₂O₃) may exceed 0.00, or may be 0.01 or more, 0.05 or more, 0.10 or more, or 0.20 or more.

[0245] From the perspective of maintaining glass stability and reducing the thermal expansion coefficient, the mass ratio of the combined content of Al2O3 and BaO to the content of Li2O ((Al2O3 + BaO) / Li2O) is 2.77 or less, preferably 2.50 or less, and more preferably 2.30 or less, 2.00 or less, 1.80 or less, and 1.60 or less. The mass ratio ((Al2O3 + BaO) / Li2O) can be, for example, 0.00, 0.00 or more, greater than 0.00, 0.10 or more, 0.50 or more, or 1.00 or more.

[0246] From the viewpoint of low dispersion of glass and reduction of thermal expansion coefficient, the mass ratio of the total content of MgO and CaO to the total content of Li2O, Na2O and KO ((MgO + CaO) / (Li2O + Na2O + KO)) is 6.10 or less, preferably 5.90 or less, and more preferably 5.80 or less, 5.70 or less, 5.60 or less, 5.50 or less, 5.40 or less, 5.30 or less, 5.20 or less, 5.10 or less, 5.50 or less, 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, 4.00 or less, 3.90 or less, 3.80 or less, and 3.70 or less in this order. The mass ratio ((MgO+CaO) / (Li2O+Na2O+K2O)) can be, for example, 0.00, 0.00 or more, more than 0.00, 0.10 or more, 0.50 or more, 1.00 or more, 2.00 or more, or 3.00 or more.

[0247] The mass ratio of the total content of SrO and BaO to the content of Li2O ((SrO+BaO) / Li2O) can be, for example, 0.00, 0.00 or more, more than 0.00, 0.01 or more, or 0.10 or more.

[0248] From the viewpoint of suppressing the increase in the coefficient of thermal expansion of the glass, the mass ratio ((SrO+BaO) / Li2O) is preferably 5.00 or less, and more preferably in the order of 4.80 or less, 4.50 or less, 4.30 or less, 4.00 or less, 3.50 or less, 3.00 or less, 2.50 or less, 2.00 or less, 1.50 or less, 1.00 or less, 0.80 or less, and 0.50 or less.

[0249] The total content of SrO, BaO and K2O (SrO+BaO+K2O) can be, for example, 0.00% or more. From the viewpoint of maintaining the stability of the glass, it is preferably more than 0.00%, and more preferably in the order of 0.10% or more and 0.50% or more.

[0250] From the viewpoint of suppressing the increase in the coefficient of thermal expansion of the glass, the total content (SrO+BaO+K2O) is preferably 13.00% or less, and more preferably 12.00% or less, 11.00% or less, 10.00% or less, 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, 1.00% or less, 0.90% or less, and 0.80% or less in this order.

[0251] ZnO is a component that contributes to improving the stability of glass and increasing the refractive index. The ZnO content may be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, or 1.00% or more.

[0252] From the viewpoint of suppressing high dispersion of glass, the ZnO content is 23.00% or less, preferably 21.00% or less, and more preferably 19.00% or less, 17.00% or less, 15.00% or less, 13.00% or less, 11.00% or less, 9.00% or less, 7.00% or less, 5.00% or less, 3.00% or less, and 1.00% or less.

[0253] The total content of ZnO and BaO (ZnO+BaO) may be, for example, 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, or 1.00% or more.

[0254] From the viewpoint of suppressing high dispersion of glass and suppressing an increase in the thermal expansion coefficient, it is preferably 20.50% or less, and more preferably in the order of 20.00% or less, 19.00% or less, 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 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.

[0255] From the perspective of maintaining the stability of the glass and reducing the thermal expansion coefficient, the mass ratio of the total content of MgO, CaO, SrO, BaO, and ZnO to the total content of P2O5, B2O3, and SiO2 ((MgO + CaO + SrO + BaO + ZnO) / (P2O5 + B2O3 + SiO2)) is 0.36 or less, preferably 0.35 or less, and more preferably 0.34 or less, 0.33 or less, 0.30 or less, 0.27 or less, 0.25 or less, and 0.24 or less in this order. The mass ratio ((MgO + CaO + SrO + BaO + ZnO) / (P2O5 + B2O3 + SiO2)) can be, for example, greater than 0.00, 0.01 or more, 0.10 or more, 0.50 or more, 1.00 or more, 1.50 or more, or 2.00 or more.

[0256] When the P2O5 content is 58.00% or more, from the viewpoint of maintaining the stability of the glass and the viewpoint of low dispersion, the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li2O, Na2O and KO ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+KO)) is preferably less than 6.00, and more preferably in the order of 5.80 or less, 5.70 or less, 5.60 or less, 5.50 or less, 5.40 or less, 5.30 or less, 5.20 or less, 5.10 or less, 5.00 or less, 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, 4.00 or less, and 3.90 or less.

[0257] When the P2O5 content is less than 58.00%, the mass ratio ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+K2O)) may be within the above range or may exceed the above range.

[0258] In any case where the P2O5 content is less than 58.00% and where the P2O5 content is greater than 58.00%, the mass ratio ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+K2O)) can be, for example, greater than 0.00, greater than 0.10, greater than 0.50, greater than 1.00, greater than 1.50, greater than 2.00, greater than 2.50 or greater than 3.00.

[0259] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) can be 0.00% or more.

[0260] From the perspective of suppressing the high dispersion of glass, the total content (La2O3+Gd2O3+Y2O3) is preferably less than 7.00%, and is preferably in the order of less than 6.50%, less than 6.00%, less than 5.00%, less than 4.00%, less than 3.00%, less than 2.00%, less than 1.00%, less than 0.50%, and less than 0.10%, and can also be 0.00%.

[0261] The content of each of La2O3, Gd2O3 and Y2O3 may be 0.00% or more.

[0262] From the perspective of suppressing the high dispersion of glass, the content of La2O3, Gd2O3 and Y2O3 is preferably less than 7.00%, and is preferably in the order of less than 6.50%, less than 6.00%, less than 5.00%, less than 4.00%, less than 3.00%, less than 2.00%, less than 1.00%, less than 0.50% and less than 0.10%, and can also be 0.00%.

[0263] The Nb2O5 content may be 0.00% or more.

[0264] From the perspective of suppressing high dispersion of glass, the Nb2O5 content is preferably less than 5.00%, and is preferably less than 4.50%, less than 4.00%, less than 3.50%, less than 3.00%, less than 2.00%, less than 1.00%, less than 0.50%, and less than 0.10% in this order, and can also be 0.00%.

[0265] The ZrO2 content may be 0.00%, 0.00% or more, more than 0.00%, or 0.10% or more.

[0266] From the viewpoint of suppressing high dispersion of glass, the ZrO2 content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in this order.

[0267] Sb2O3 is a component that can be added as a clarifier. While a small amount can suppress the reduction in light transmittance caused by the incorporation of impurities such as Fe, increasing the amount of Sb2O3 added tends to increase the coloration of the glass. Therefore, the amount of Sb2O3 added is preferably 0.00% to 0.15% on an added basis, more preferably 0.00% to 0.12%, even more preferably 0.00% to 0.10%, and even more preferably 0.00% to 0.05%. The Sb2O3 content on an added basis refers to the Sb2O3 content expressed in mass % when the total content of the glass components other than Sb2O3 is taken as 100% by mass.

[0268] SnO2 can also be added as a clarifier, but if added in an amount exceeding 1.00% as a percentage, it can cause coloration of the glass or, when the glass is heated, softened, and then remolded by press molding, Sn can become a starting point for crystal nucleation, leading to a tendency for devitrification. Therefore, the amount of SnO2 added is preferably between 0.00% and 1.00%, more preferably between 0.00% and 0.50%, and particularly preferably not added. The SnO2 content as a percentage is the amount expressed in mass % when the total content of the glass components other than SnO2 is taken as 100% by mass.

[0269] From the viewpoint of environmental impact, glass A preferably contains substantially no Pb. In glass containing substantially no Pb, the PbO content is preferably 0.00% or more and less than 0.01%.

[0270] From the perspective of effectively utilizing the excellent light transmittance of glass, glass A preferably contains substantially no coloring components. In the present invention and this specification, the term "coloring component" for glass A refers to one or more selected from the group consisting of Ti, Cu, Cr, V, Fe, Ni, and Co. In glass A, the content of the coloring components as oxides (or the total content if two or more are included) is preferably 0.00% or more and less than 0.01%.

[0271] F is a component that significantly increases the volatility of glass during melting, causing a decrease in the stability and homogeneity of the glass's optical properties. Therefore, it is preferred that Glass A contain substantially no F. The F content can also be specified as the added proportion (unit: mass %) of the F element relative to 100% by mass of the total content of the glass composition based on oxides as determined above. In Glass A, the F content thus specified is preferably less than 0.10%, more preferably less than 0.08%, and even more preferably less than 0.05%. The F content may be 0.00% or higher, or even 0.00%.

[0272] (Glass B)

[0273] Hereinafter, the glass composition of Glass B will be described in more detail.

[0274] The SiO2 content may be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, or 0.10% or more.

[0275] SiO2 is a glass structure-forming component. From the perspective of maintaining glass stability and weather resistance, the SiO2 content is 5.00% or less, preferably 4.00% or less, and more preferably 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less, in this order.

[0276] B2O3 is a glass structure forming component. The B2O3 content may be 0.00%, 0.00% or more, or more than 0.00%.

[0277] B2O3 is also a component that contributes to increasing the value of the temperature coefficient of refractive index dn / dT (also abbreviated as "dn / dT"). dn / dT will be described below.

[0278] The temperature coefficient of refractive index dn / dT in the present invention and this specification is the temperature coefficient of the relative refractive index at a wavelength of 632.8 nm specified in the Japan Optical Glass Industry Association Standard JOGIS18-2019 "Method for Determination of the Temperature Coefficient of Refractive Index of Optical Glass", and is a value measured by interferometry.

[0279] In various optical systems, such as imaging systems and projection systems, chromatic aberration is corrected by fabricating multiple lenses made of optical glass with different optical properties and combining these lenses to form an optical system. By combining lenses made of optical glass with a positive dn / dT value (i.e., a value greater than zero) with lenses made of optical glass with a negative dn / dT value (i.e., a value less than zero) to form such an optical system, the individual lenses can offset the effects of temperature changes on the entire optical system. As a result, the performance of the optical system (e.g., imaging performance) can be maintained at an excellent state despite temperature changes. Conventionally, phosphate-based glass often exhibits a negative dn / dT value, so phosphate-based glass with a positive dn / dT value is more useful. In contrast, one embodiment of the optical glass of the present invention can exhibit a positive dn / dT value (i.e., "dn / dT" > 0).

[0280] From the viewpoint of maintaining the weather resistance of the glass and increasing the dn / dT value, the B2O3 content is preferably 0.05% or more, and more preferably 0.10% or more, 1.00% or more, 2.00% or more, and 3.00% or more in this order.

[0281] On the other hand, from the perspective of low dispersion, high refractive index and weather resistance of glass, the B2O3 content is less than 20.00%, preferably less than 18.00%, and more preferably less than 16.00%, less than 14.00%, less than 12.50%, less than 12.00%, less than 10.00% and less than 8.00%.

[0282] In glass B-2, the B2O3 content is 0.00% or more and 12.50% or less. In glass B-2, from the perspective of maintaining glass stability, when the P2O5 content is 77.00% or more and the Al2O3 content is 14.00% or more and 30.00% or less, the B2O3 content is 4.75% or more and 12.50% or less.

[0283] Glass B is a phosphate glass and therefore contains P₂O₅. P₂O₅ is also a glass structure-forming component. From the perspective of achieving low dispersion, the P₂O₅ content is 60.00% or greater, preferably 62.00% or greater, with 64.00% or greater, 66.00% or greater, 68.00% or greater, 70.00% or greater, 71.00% or greater, and 72.00% or greater being more preferred in this order.

[0284] On the other hand, from the viewpoint of maintaining weather resistance, the P2O5 content is preferably 80.00% or less, and more preferably 79.50% or less, 79.00% or less, 78.80% or less, 78.60% or less, and 78.50% or less in this order.

[0285] However, from the viewpoint of reducing the dispersion of the glass, when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more.

[0286] In glass B-1, the P2O5 content is 80.00% or less, preferably 79.50% or less, and more preferably 79.00% or less, 78.80% or less, 78.60% or less, and 78.50% or less in this order.

[0287] However, from the viewpoint of reducing the dispersion of the glass, in glass B-1, when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more and 80.00% or less.

[0288] Al2O3 is a component that can improve the weather resistance of glass. From the perspective of maintaining the weather resistance of glass, the Al2O3 content is 1.00% or more, preferably 2.00% or more, and more preferably 3.00% or more and 4.00% or more in this order.

[0289] On the other hand, from the perspective of maintaining the stability of the glass, the Al2O3 content is 30.00% or less, preferably 25.00% or less, and more preferably 20.00% or less, 18.00% or less, 16.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, and 10.00% or less.

[0290] From the perspective of further improving the weather resistance of glass, when the P2O5 content is 77.00% or more, the Al2O3 content is preferably 11.00% or more and 30.00% or less. In glass B-2, when the P2O5 content is 77.00% or more, the Al2O3 content is 11.00% or more and 30.00% or less, preferably 11.00% or more and 14.00% or less. In glass B-1, when the P2O5 content is 77.00% or more and 80.00% or less, the Al2O3 content is preferably 11.00% or more and 14.00% or less.

[0291] In glass B-2, from the viewpoint of maintaining glass stability, when the CaO content is 0.50% or more and 15.00% or less, the Al 2 O 3 content is preferably 1.00% or more and less than 14.00%.

[0292] In glass B-2, the P2O5 content is 60.00% or more and less than 77.0%, or the P2O5 content is 77.00% or more and the Al2O3 content is 11.00% or more and 30.00% or less.

[0293] From the perspective of maintaining the stability of the glass, the total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is above 71.00%, preferably above 72.00%, and more preferably above 73.00%, above 74.00%, above 75.00% and above 76.00%.

[0294] From the viewpoint of suppressing a decrease in the refractive index of the glass, the total content (SiO2+B2O3+P2O5+Al2O3) is preferably 99.00% or less, more preferably 98.00% or less and then 97.00% or less.

[0295] The mass ratio of the Al2O3 content to the P2O5 content (Al2O3 / P2O5) may exceed 0.00, be 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, or 0.09 or more.

[0296] From the viewpoint of maintaining the stability of the glass, the mass ratio of the Al2O3 content to the P2O5 content (Al2O3 / P2O5) is preferably 0.20 or less, and more preferably 0.19 or less, 0.18 or less, and 0.17 or less in this order.

[0297] Li2O contributes to lowering the glass transition temperature (Tg), reducing the coefficient of thermal expansion, achieving low dispersion, increasing the refractive index, and increasing the dn / dT value. The Li2O content is 0.00% or higher, preferably exceeding 0.00%, and more preferably 0.10% or higher, 0.50% or higher, 1.00% or higher, and finally 1.50% or higher, in that order.

[0298] From the viewpoint of maintaining the stability and weather resistance of the glass, the Li2O content is preferably 10.00% or less, and more preferably 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, and 4.00% or less in this order.

[0299] Na2O is a component that helps lower the glass transition temperature Tg, reduce the thermal expansion coefficient, achieve low dispersion, and increase the dn / dT value. The Na2O content can be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, or 0.10% or more.

[0300] From the viewpoint of suppressing the decrease in the refractive index of the glass and maintaining weather resistance, the Na2O content is preferably 5.00% or less, and more preferably 4.50% or less, 4.00% or less, 3.50% or less, 3.00% or less, and 2.50% or less.

[0301] K2O is a component that helps lower the glass transition temperature Tg and improve weather resistance. The K2O content may be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, or 0.10% or more.

[0302] From the viewpoint of suppressing the decrease in the refractive index of the glass, the K2O content is 5.00% or less, preferably 4.00% or less, and more preferably 3.00% or less, 2.50% or less, 2.00% or less, 1.50% or less, and 1.00% or less in this order.

[0303] From the viewpoint of increasing the refractive index of the glass, the total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is 1.40% or more, preferably 1.60% or more, and more preferably 1.80% or more and 2.00% or more in that order.

[0304] On the other hand, from the viewpoint of maintaining the stability of the glass, the total content (Li2O+Na2O+K2O) is 6.00% or less, preferably 5.90% or less, and more preferably 5.80% or less, 5.70% or less, and 5.60% or less in this order.

[0305] In one embodiment, from the perspective of increasing the refractive index of the glass and reducing the thermal expansion coefficient, when the total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is greater than 96.00%, the total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is preferably greater than 2.10% and less than 6.00%.

[0306] MgO is a component that contributes to improving the weather resistance of glass. The MgO content may be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, 0.10% or more, 0.50% or more, or 1.00% or more.

[0307] From the viewpoint of reducing dispersion of glass and maintaining weather resistance, the MgO content is 10.00% or less, preferably 9.00% or less, more preferably 8.00% or less, and then 7.00% or less in this order.

[0308] CaO is a component that contributes to improving the weather resistance of glass. The CaO content may be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, 0.10% or more, 0.50% or more, or 1.00% or more.

[0309] From the viewpoint of reducing dispersion of glass and maintaining weather resistance, the CaO content is 15.00% or less, preferably 14.00% or less, and more preferably 13.00% or less, 12.00% or less, and 11.00% or less in this order.

[0310] In glass B-2, the CaO content may be 0.00% to less than 0.50%, or 0.50% to 15.00%. As described above, when the CaO content is 0.50% to 15.00%, the Al2O3 content is preferably 1.00% to less than 14.00%.

[0311] From the perspective of maintaining glass stability, the mass ratio of the Li₂O content to the Al₂O₃ content (Li₂O / Al₂O₃) is preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less. The mass ratio (Li₂O / Al₂O₃) may be 0.00 or greater, 0.01 or greater, 0.03 or greater, or 0.05 or greater. In glass B-2, when the Al₂O₃ content is 14.00% or greater, the mass ratio of the Li₂O content to the Al₂O₃ content (Li₂O / Al₂O₃) is preferably 0.13 or less.

[0312] SrO is a component that contributes to increasing the refractive index of glass. The SrO content may be 0.00%, 0.00% or more, or more than 0.00%.

[0313] From the viewpoint of reducing dispersion of glass and maintaining weather resistance, the SrO content is 5.00% or less, preferably 4.00% or less, and more preferably 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in this order.

[0314] BaO is a component that contributes to increasing the refractive index of glass. The BaO content may be 0.00%, 0.00% or more, or more than 0.00%.

[0315] From the viewpoint of reducing dispersion of glass and maintaining weather resistance, the BaO content is 5.00% or less, preferably 4.00% or less, and more preferably 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in this order.

[0316] ZnO is a component that contributes to improving the weather resistance of glass. The ZnO content may be 0.00%, 0.00% or more, or more than 0.00%.

[0317] From the viewpoint of reducing the dispersion of glass, the ZnO content is 5.00% or less, preferably 4.50% or less, and more preferably 4.00% or less, 3.50% or less, and 3.10% or less in this order.

[0318] The total content of MgO and CaO (MgO + CaO) can be 0.00%, 0.00% or more, or more than 0.00%. The total content (MgO + CaO) can be, for example, 25.00% or less or 20.00% or less. In one embodiment, from the perspective of increasing the refractive index of the glass and reducing dispersion, when the total content (MgO + CaO) is 0.00%, the Li2O content is preferably 3.10% or more.

[0319] From the perspective of further improving the weather resistance of glass, when the B2O3 content is 0.00% or more and less than 3.00%, the total content of MgO and CaO (MgO+CaO) is preferably 10.10% or more. Alternatively, the B2O3 content is 3.00% or more and 20.00% or less.

[0320] In glass B-2, when the B2O3 content is 0.00% or more and less than 3.00%, the total content of MgO and CaO (MgO+CaO) is 10.10% or more. Alternatively, in glass B-2, the B2O3 content is 3.00% or more and 12.50% or less.

[0321] In addition, from the viewpoint of further improving the weather resistance of glass, when the total content of MgO and CaO (MgO+CaO) is 0.00% to 3.00%, the Al2O3 content is preferably 7.00% to 30.00%.

[0322] In glass B-1, when the total content of MgO and CaO (MgO+CaO) is 0.00% to 3.00%, the Al 2 O 3 content is preferably 7.00% to 14.00%.

[0323] The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) can be 0.00%, 0.00% or more, or more than 0.00%. La2O3, Y2O3 and Gd2O3 are all components that contribute to increasing the refractive index of glass.

[0324] From the perspective of low dispersion of glass, the total content (La2O3+Y2O3+Gd2O3) is 4.00% or less, preferably 3.00% or less, and more preferably 2.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less in this order.

[0325] From the perspective of low dispersion of glass, when the total content (La2O3+Y2O3+Gd2O3) exceeds 0.00% and is 4.00% or less, the total content of P2O5 and B2O3 (P2O5+B2O3) is preferably greater than 80.00%.

[0326] In any case where the total content (La2O3+Y2O3+Gd2O3) is 0.00% or exceeds 0.00% and is 4.00% or less, the total content (P2O5+B2O3) can be, for example, 90.00% or less.

[0327] The content of each of La2O3, Y2O3 and Gd2O3 may be 0.00%, 0.00% or more, or more than 0.00%.

[0328] The content of each of La2O3, Y2O3 and Gd2O3 can be, for example, 4.00% or less, 3.00% or less, 2.00% or less, 1.50% or less, 1.00% or less or 0.50% or less.

[0329] The ZrO2 content may be 0.00%, 0.00% or more, more than 0.00%, or 0.10% or more.

[0330] From the viewpoint of low dispersion of glass, the ZrO2 content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in this order.

[0331] Sb2O3 is a component that can be added as a clarifier. While a small amount can suppress the reduction in transmittance caused by the incorporation of impurities such as Fe, increasing the Sb2O3 content tends to increase the coloration of the glass. Therefore, the Sb2O3 content, as measured by the added percentage, is preferably from 0.00% to 0.15%, and more preferably from 0.00% to 0.12%. The Sb2O3 content, as measured by the added percentage, refers to the Sb2O3 content expressed in mass % when the total content of the glass components other than Sb2O3 is taken as 100% by mass. When glass B contains Sb2O3, the Sb2O3 content can be 0.01% or more as measured by the added percentage. For example, the Sb2O3 content of glass B-2 can be 0.01% or more as measured by the added percentage.

[0332] SnO2 can also be added as a clarifier, but if added in excess of 1.00%, it can cause coloration of the glass or, when the glass is heated, softened, and then remolded by press molding, Sn can become a starting point for crystal nucleation, leading to devitrification. Therefore, the SnO2 content is preferably between 0.00% and 1.00%, more preferably between 0.00% and 0.50%, and particularly preferably not added. The SnO2 content, as added, refers to the amount of SnO2 expressed in mass % when the total amount of the glass components other than SnO2 is taken as 100% by mass.

[0333] From the viewpoint of environmental impact, it is preferred that glass B contain substantially no Pb. In glass containing substantially no Pb, the PbO content is preferably 0.00% or more and less than 0.01%.

[0334] From the perspective of reducing dispersion and suppressing coloration, the CuO content of glass B is preferably less than 0.50%, more preferably 0.40% or less, 0.30% or less, 0.20% or less, and 0.10% or less, in this order, and even more preferably 0.00%. The CuO content of glass B-2 is 0.00% or more and less than 0.50%.

[0335] From the perspective of effectively utilizing the excellent light transmittance of glass, glass B preferably contains substantially no coloring components. In the present invention and this specification, the term "coloring component" for glass B refers to at least one selected from the group consisting of Cu, Nd, Ce, Tb, Er, As, Ag, Sn, and Fe. In glass B, the content of the coloring components as oxides (or the total content if two or more are present) is preferably 0.00% or more and less than 0.01%.

[0336] F is a component that significantly increases the volatility of glass during melting, causing a decrease in the stability and homogeneity of the glass's optical properties. Therefore, it is preferred that the optical glass described above contain substantially no F. The F content can also be specified as the added proportion (unit: mass %) of the F element relative to 100% by mass of the total content of the glass composition based on oxides as determined above. In glass B, the F content thus specified is preferably less than 0.10%, more preferably less than 0.08%, and even more preferably less than 0.05%. The F content can be 0.00% or more, or even 0.00%.

[0337] <Glass Properties>

[0338] (Coefficient of thermal expansion)

[0339] Glass A has the glass composition described above and can exhibit a low thermal expansion coefficient. As an indicator of the thermal expansion coefficient, the average linear expansion coefficient α at 100°C to 300°C can be cited. Hereinafter, the average linear expansion coefficient α at 100°C to 300°C will also be described as "α(100 / 300)". α(100 / 300) of Glass A is 130×10 -7 / K or less, 125×10 -7 / K or less, 120×10 -7 / K or less, 115×10 -7 / K or less, 110×10 -7 / K or less is more preferable. α(100 / 300) can be, for example, 70×10 -7 / K or above, 75×10 -7 / K or above or 80×10 -7 / K or above, but can also be lower than the value shown here.

[0340] Glass B has the glass composition described above and can exhibit a low thermal expansion coefficient. As an indicator of the thermal expansion coefficient, the average linear expansion coefficient α at -30°C to 70°C can be cited. The average linear expansion coefficient α at -30°C to 70°C is also described as "α(-30 / 70)". α(-30 / 70) of Glass B is 90×10 -7 / K or less, 89×10 -7 / K or less, 88×10 -7 / K or less, 87×10 -7 / K or less, 80×10 -7 / K or less, 85×10 -7 / K or less, 84×10 -7 / K or less, 83×10 -7 / K or less is more preferable. α(-30 / 70) can be, for example, 50×10 -7 / K or above or 55×10 -7 / K or above, or lower than the value shown here.

[0341] The α(100 / 300) of glass B is preferably 120×10 -7 / K or less, 115×10 -7 / K or less, 110×10 -7 / K or less, 105×10 -7 The order of α(100 / 300) of glass B can be, for example, 60×10 -7 / K or above or 65×10 -7 / K or above, but can also be lower than the value shown here.

[0342] The average linear expansion coefficient α at -30°C to 70°C and the average linear expansion coefficient α at 100°C to 300°C can be measured by the method specified in Japan Optical Glass Industry Association Standard JOGIS 08-1975, "Measurement Method of Thermal Expansion of Optical Glass." For example, the measurement can be performed using a TMA8311 thermomechanical analyzer manufactured by Rigaku Corporation, using a cylindrical glass sample having a diameter of 5 mm and a length of 20 mm.

[0343] (Abbe number νd)

[0344] Glass A, by having the above-described glass composition, exhibits low dispersion. The Abbe number νd, an indicator of dispersion, can be expressed as νd = (nd-1) / (nF-nC) using the refractive indices nd, nF, and nC under d-rays, F-rays, and C-rays, respectively. From the perspective of its usefulness as a material for optical elements, the Abbe number νd of Glass A is 60.00 or greater, preferably 62.00 or greater, and more preferably 64.00 or greater. The Abbe number νd of Glass A can be, for example, 80.00 or less, 75.00 or less, or 70.00 or less, but may also be higher than the values ​​exemplified here.

[0345] Glass B, having the above-described glass composition, can exhibit low dispersion. From the perspective of usefulness as a material for optical elements, the Abbe number νd of Glass B is 65.00 or greater, preferably 66.00 or greater, and more preferably 67.00 or greater. The Abbe number νd of Glass B can be, for example, 80.00 or less, 78.00 or less, 76.00 or less, 74.00 or less, or 72.00 or less, but may also be higher than the values ​​exemplified here.

[0346] (refractive index nd)

[0347] From the perspective of usefulness as a material for optical elements, the refractive index nd of Glass A is 1.70,000 or less, preferably 1.65,000 or less, and more preferably 1.60,000 or less and 1.55,000 or less, in that order. The refractive index nd can be, for example, 1.45,000 or greater, 1.46,000 or greater, 1.47,000 or greater, 1.48,000 or greater, 1.49,000 or greater, or 1.50,000 or greater. In the present invention and this specification, "refractive index" refers to "refractive index nd." The refractive index nd represents the refractive index at a wavelength of 587.56 nm.

[0348] From the perspective of usefulness as a material for optical elements, the refractive index nd of glass B is 1.49000 or greater, preferably 1.50000 or greater, and more preferably 1.51000 or greater. From the perspective of usefulness as a material for optical elements, the refractive index nd of glass B is preferably 1.65000 or less, more preferably 1.60000 or less and then 1.56000 or less, in that order.

[0349] (proportion)

[0350] From the perspective of lightweighting optical elements, optical glass preferably has a low specific gravity. The specific gravity of glass A and glass B can be, for example, 3.00 g / cc or less, 2.90 g / cc or less, or 2.80 g / cc or less. Alternatively, the specific gravity of glass A and glass B can be, for example, 2.00 g / cc or greater. A lower specific gravity is preferred, so there is no particular lower limit. Specific gravity can be determined using the Archimedean method.

[0351] (Glass transition temperature Tg)

[0352] Glass A, having the above-described glass composition, can exhibit a glass transition temperature (Tg) of, for example, 550°C or less, 540°C or less, 530°C or less, 520°C or less, 510°C or less, or 500°C or less. The glass transition temperature (Tg) of Glass A can be, for example, 300°C or more or 400°C or more, but may also be lower than the values ​​exemplified here. The glass transition temperature (Tg) can be determined by the method described below.

[0353] Glass B, having the above-described glass composition, can exhibit a glass transition temperature (Tg) of, for example, 600°C or less, 590°C or less, 580°C or less, 570°C or less, 560°C or less, or 550°C or less. The glass transition temperature (Tg) of glass B can be, for example, 300°C or more or 400°C or more, but may also be lower than the values ​​exemplified here.

[0354] (Transmittance characteristics)

[0355] The external transmittance of glass A and glass B at a wavelength of 400nm to 700nm is preferably 60% or more when converted to a thickness of 10.0mm. "External transmittance at a wavelength of 400nm to 700nm is 60% or more when converted to a thickness of 10.0mm" means that the external transmittance over the entire wavelength range of 400nm to 700nm is 60% or more when converted to a thickness of 10.0mm. The external transmittance of glass A and glass B at a wavelength of 400nm to 700nm can be 60% or more and 100% or less when converted to a thickness of 10.0mm. Optical glass with such transmittance characteristics is useful as a material for optical elements. For example, the above transmittance characteristics can be achieved by making the glass substantially free of coloring components.

[0356] The transmittance characteristics of the above-mentioned glass can be obtained by the following method.

[0357] Glass samples are processed into parallel, optically polished surfaces, and their external transmittance is measured at wavelengths between 400 and 700 nm. The external transmittance also includes light reflection losses at the sample surface.

[0358] When the glass to be measured is not 10.0 mm thick, the thickness of the glass to be measured is set to d0, and the transmittance at each wavelength λ is converted using the following formula A to obtain transmittance characteristics converted to a thickness of 10.0 mm.

[0359] Formula A: T(λ)=(1-R(λ))2×exp(loge((T0(λ) / 100) / (1-R(λ))2)×d / d0)×100

[0360] In formula A, T(λ) is the converted transmittance at wavelength λ (%), T0(λ) is the measured transmittance at wavelength λ (%), d is the thickness to be converted (mm), d0 is the thickness of the glass (mm), and R(λ) = ((n(λ)-1) / (n(λ)+1)) 2 Reflectance at wavelength λ, n(λ): Refractive index at wavelength λ. The refractive index n(λ) at wavelength λ was measured according to Japanese Industrial Standards (JIS) JIS B 7071-1, "Optical Glass - Determination of Refractive Index - Part 1: Minimum Deviation Angle Method," at each wavelength.

[0361] (The difference in fogging value before and after the weathering test D H )

[0362] The difference in fog value before and after the weathering test D H (Also referred to as "D H ”) can be used as an indicator of weather resistance.

[0363] In the weathering test, a 30 mm x 30 mm x 3 mm glass sample that had been polished on its surface was subjected to a temperature cycle test under high temperature and high humidity conditions as specified in the Japan Optical Glass Industry Association standard JOGIS07-2009. The difference in haze (haze, %) between the glass sample before and after the test was determined. The smaller the difference, the better the weathering resistance. In JOGIS07-2009, one cycle is set to 2 hours, and the treatment time of the temperature cycle test is specified to be 24 cycles, or 48 hours. It should be noted that the haze can be measured using a haze meter as described in JIS K 7136:2000.

[0364] Glass B has the glass composition described in detail above and can show excellent weather resistance. H (Unit: %) Achieve weather resistance of 0.0% or more and 5.0% or less. D HIt is preferably less than 4.5%, and more preferably in the order of less than 4.0%, less than 3.5%, less than 3.0%, less than 2.5%, less than 2.0%, less than 1.5%, less than 1.0%, less than 0.5%, less than 0.3%, and less than 0.1%. The smaller the better, and the most preferred is 0.0%.

[0365] (Temperature coefficient of refractive index dn / dT)

[0366] In one embodiment, the temperature coefficient of the refractive index of glass B, dn / dT, may exceed 0°C. -1 If dn / dT exceeds 0℃ -1 , that is, optical glass with a positive value, then such optical glass can offset or reduce the influence of temperature changes on the entire optical system through each lens as described above.

[0367] dn / dT can be calculated by the following method.

[0368] A disc-shaped sample with a diameter of 20 mm and a thickness of 5 mm was prepared. Using a He-Ne gas laser, the temperature coefficient of the relative refractive index, dn / dT, at a wavelength of 632.8 nm was measured by interferometry in accordance with the Japan Optical Glass Manufacturers' Association standard JOGIS 18-2019, "Determination of the Temperature Coefficient of the Refractive Index of Optical Glass." Specifically, within the temperature range of -40°C to 150°C, the sample temperature was increased from -40°C to 140°C in 20°C increments and then from 140°C to 150°C in 10°C increments (heating rate: approximately 1°C / minute). The temperature coefficient of the refractive index, dn / dT, at temperatures between 20°C and 40°C was determined based on the results of continuous measurements of the sample temperature and the number of interference fringes.

[0369] <Method for manufacturing optical glass>

[0370] The above-mentioned optical glass can be obtained by the following method, for example. In order to obtain the target glass composition, phosphate, fluoride, oxide, carbonate, sulfate, nitrate, hydroxide etc. as raw materials are weighed and allocated, and fully mixed to prepare a mixed batch (allocation raw material). The prepared mixed batch is heated and melted in a melting vessel, and deaerated and stirred to obtain a homogeneous and bubble-free molten glass. Molten glass can be made by a known melting method. By shaping the molten glass obtained, the above-mentioned optical glass can be obtained.

[0371] [Glass material for press molding, optical element blank, and method for producing the same]

[0372] Another aspect of the present invention relates to:

[0373] Glass raw materials for press molding made from the above optical glass;

[0374] Optical element blanks made of the above optical glass.

[0375] According to another aspect of the present invention, there is also provided:

[0376] A method for producing a glass material for press molding, comprising: forming the optical glass into the glass material for press molding;

[0377] A method for manufacturing an optical element blank, comprising: press-molding the glass raw material for press-molding optical glass using a press-molding die to produce the optical element blank;

[0378] A method for manufacturing an optical element blank comprises the step of shaping the optical glass into the optical element blank.

[0379] An optical element blank is an optical element base material that approximates the shape of the target optical element and to which a polishing material (a surface layer that is removed by polishing) and, if necessary, a grinding material (a surface layer that is removed by grinding) are added. The optical element is finely processed by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by press-molding molten glass obtained by melting an appropriate amount of the above-mentioned glass (referred to as the direct press method). In another embodiment, the optical element blank can also be produced by solidifying the molten glass obtained by melting an appropriate amount of the above-mentioned glass.

[0380] In another embodiment, an optical element blank can be produced by preparing a glass material for press molding and press molding the prepared glass material for press molding.

[0381] The press-molding of the glass material for press molding can be performed by a known method of pressurizing the heated, softened glass material using a press-molding mold. Both heating and press molding can be performed in the atmosphere. Annealing after press molding reduces strain within the glass, resulting in a homogeneous optical element blank.

[0382] Press-molding glass materials include materials that are directly supplied to the press molding process for producing optical element blanks in their original form, known as press-molding glass gobs. These materials also include materials that have undergone mechanical processing such as cutting, grinding, and polishing and then passed through press-molding glass gobs before being supplied to the press molding process. Cutting methods include: creating grooves in the desired cut area on the surface of a glass sheet using a process known as scribing, applying localized pressure to the grooved area from the back of the grooved surface, and then cutting the glass sheet at the grooved area; and cutting the glass sheet with a cutting blade. Grinding and polishing methods include barrel polishing.

[0383] Glass raw materials for press molding can be produced, for example, by casting molten glass into a mold and forming it into a glass sheet, which is then cut into multiple glass sheets. Alternatively, a suitable amount of molten glass can be formed into glass gobs for press molding. Optical element blanks can also be produced by reheating and softening the glass gobs for press molding and then press molding them. The method of reheating, softening, and press molding the glass to produce optical element blanks is known as the reheat press method, as opposed to the direct press method.

[0384] [Optical element and method of manufacturing the same]

[0385] Another embodiment of the present invention relates to an optical element made of the above-mentioned optical glass.

[0386] The optical element is made of the optical glass. In the optical element, one or more coating layers such as a multilayer film such as an antireflection film may be formed on the glass surface.

[0387] According to one embodiment of the present invention, there is provided a method for manufacturing an optical element, comprising the step of manufacturing the optical element by grinding and / or polishing the optical element blank.

[0388] In the above-mentioned method for manufacturing an optical element, mechanical processing such as grinding and polishing can be performed using known methods. By thoroughly cleaning and drying the surface of the optical element after processing, an optical element with high internal and surface quality can be obtained. In this way, an optical element made of the above-mentioned optical glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, as well as prisms.

[0389] In addition, the optical element made of the above-mentioned optical glass is also suitable for use as a lens constituting a bonded optical element. As a bonded optical element, an element formed by bonding lenses to each other (bonded lens), an element formed by bonding a lens to a prism, etc. can be exemplified. For example, a bonded optical element can be produced by the following method: the bonding surfaces of the two optical elements to be bonded are precisely processed in such a way that their shapes become inverted shapes (for example, spherical polishing), and an ultraviolet curing adhesive for bonding the bonding lenses is applied, and after they are bonded, the adhesive is cured by irradiating ultraviolet rays through the lens, thereby producing a bonded optical element. A plurality of optical elements to be bonded can be produced separately using a variety of glasses with different Abbe numbers νd, and bonded, thereby producing an element suitable for chromatic aberration correction.

[0390] Example

[0391] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the embodiments shown in the Examples.

[0392] [Example 1]

[0393] Sample No. 1 to 168

[0394] In order to obtain the glass composition shown in the table below, corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component, and the raw materials are weighed and thoroughly mixed to prepare a mixed raw material.

[0395] The prepared raw materials were placed in a platinum crucible and heated in a furnace set at 1100-1350°C, melting for 120 minutes. The molten glass was stirred and homogenized, then poured into a preheated mold. After naturally cooling to near the glass transition temperature, the molten glass was immediately placed in an annealing furnace. After being held at a temperature around the glass transition temperature for approximately 30 minutes, the molten glass was slowly cooled at a slow cooling rate of -30°C / hour for 4 hours, and then naturally cooled in the furnace to room temperature. This yielded the optical glasses of Samples Nos. 1-168 shown in Tables 1-7 below. The optical glasses of Samples Nos. 1-168 shown in Tables 1-7 below correspond to Glass A.

[0396] <Physical property evaluation>

[0397] Various physical properties of each optical glass shown in Tables 1 to 7 described below were measured by the following methods.

[0398] (1) Average linear expansion coefficient α at 100℃~300℃

[0399] The average linear expansion coefficient α of each optical glass at 100°C to 300°C was measured using the method specified in Japan Optical Glass Manufacturers' Association Standard JOGIS 08-1975, "Measurement Method of Thermal Expansion of Optical Glass." Specifically, cylindrical glass samples with a diameter of 5 mm and a length of 20 mm were prepared and measured using a TMA8311 thermomechanical analyzer manufactured by Rigaku Corporation.

[0400] (2) Refractive index nd, Abbe number νd

[0401] The refractive index nd and the Abbe number νd of each optical glass were measured by the refractive index measurement method according to the Japan Optical Glass Manufacturers Association standard.

[0402] (3) Specific gravity

[0403] The specific gravity was measured by the Archimedean method.

[0404] (4) Glass transition temperature Tg

[0405] Glass was thoroughly pulverized in a mortar as a sample, and the glass transition temperature Tg was measured using a differential scanning calorimeter (DSC8271) manufactured by Rigaku Corporation at a heating rate of 10°C / min using a platinum cell as a sample container.

[0406] (5) Transmittance characteristics

[0407] A test piece was cut out from the obtained glass, and both surfaces were mirror-polished to have parallel optically polished flat surfaces to a thickness of 10.0 mm. The external transmittance at a wavelength of 400 to 700 nm was measured using a spectrophotometer.

[0408] For all samples No. 1 to 168 shown in Tables 1 to 7 described later, it was confirmed that the external transmittance at a wavelength of 400 nm to 700 nm was 60% or more and 100% or less at a thickness of 10.0 mm.

[0409] The above results are shown in the following table. In the table, the unit of the content of the glass component is mass %.

[0410] "○" in the table indicates that the items described in the title of the column marked with "○" are satisfied.

[0411]

[0412]

[0413]

[0414]

[0415]

[0416]

[0417]

[0418]

[0419]

[0420]

[0421]

[0422]

[0423]

[0424]

[0425]

[0426]

[0427]

[0428]

[0429]

[0430]

[0431]

[0432]

[0433]

[0434]

[0435]

[0436]

[0437]

[0438] [Table 4-1]

[0439]

[0440] [Table 4-2]

[0441]

[0442] [Table 4-3]

[0443]

[0444] [Table 4-4]

[0445]

[0446] [Table 4-5]

[0447]

[0448] [Table 4-6]

[0449]

[0450] [Table 4-7]

[0451]

[0452] [Table 4-8]

[0453]

[0454] [Table 4-9]

[0455]

[0456]

[0457]

[0458]

[0459]

[0460]

[0461]

[0462]

[0463]

[0464]

[0465] [Table 6-1]

[0466]

[0467] [Table 6-2]

[0468]

[0469] [Table 6-3]

[0470]

[0471] [Table 6-4]

[0472]

[0473] [Table 6-5]

[0474]

[0475] [Table 6-6]

[0476]

[0477] [Table 6-7]

[0478]

[0479] [Table 6-8]

[0480]

[0481] [Table 6-9]

[0482]

[0483] [Table 7-1]

[0484]

[0485] [Table 7-2]

[0486]

[0487] [Table 7-3]

[0488]

[0489] [Table 7-4]

[0490]

[0491] [Table 7-5]

[0492]

[0493] [Table 7-6]

[0494]

[0495] [Table 7-7]

[0496]

[0497] [Table 7-8]

[0498]

[0499] [Table 7-9]

[0500]

[0501] [Example 2]

[0502] <Sample No. 1 to 47>

[0503] In order to obtain the glass compositions shown in Tables 8 to 14 described later, corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component, and the raw materials are weighed and thoroughly mixed to prepare the formulated raw materials.

[0504] The prepared raw materials were placed in a platinum crucible and heated in a furnace set at 1100-1350°C to melt for 120 minutes. After stirring and homogenizing the molten glass, the molten glass was poured into a preheated mold and naturally cooled to near the glass transition temperature. Immediately after being placed in an annealing furnace, the molten glass was maintained at a temperature around the glass transition temperature for about 30 minutes, then slowly cooled at a slow cooling rate of -30°C / hour for 4 hours, and then naturally cooled in the furnace to room temperature. This yielded the optical glasses of Samples Nos. 1 to 47 shown in Tables 8 to 14 described below.

[0505] The optical glasses of Sample Nos. 1 to 47 shown in Tables 8 to 14 described below correspond to "Glass B" and "Glass B-2." Sample Nos. 1 to 32, 34, 38, 39, and 43 to 45 shown in Tables 8 to 14 described below also correspond to Glass B-1.

[0506] <Physical property evaluation>

[0507] The refractive index nd, Abbe number νd, specific gravity, and glass transition temperature Tg of each optical glass shown in Tables 8 to 14 described below were measured by the method described above in Example 1.

[0508] The transmittance characteristics of each optical glass shown in Tables 8 to 14 below were measured using the method described above for Example 1. For all of Samples Nos. 1 to 45 shown in Tables 8 to 14 below, it was confirmed that the external transmittance at a wavelength of 400 nm to 700 nm was 60% or higher and 100% or lower at a thickness of 10.0 mm.

[0509] Furthermore, various physical properties of each optical glass shown in Tables 8 to 14 described later were measured by the following methods.

[0510] (1)α(-30 / 70),α(100 / 300)

[0511] For each optical glass, the average linear expansion coefficient α (-30 / 70) at -30°C to 70°C and the average linear expansion coefficient α (100 / 300) at 100°C to 300°C were measured using the method specified in the Japan Optical Glass Industry Association Standard JOGIS 08-1975, "Methods for Determination of Thermal Expansion of Optical Glass." Specifically, cylindrical glass samples with a diameter of 5 mm and a length of 20 mm were prepared and measured using a TMA8311 thermomechanical analyzer manufactured by Rigaku Corporation.

[0512] (2) The difference in fogging value before and after the weathering test (D) H

[0513] As an index of weather resistance, D was obtained by the method described in detail above. H (%). Specifically, a 30 mm × 30 mm × 3 mm glass sample with its surface polished was subjected to a temperature cycle test under high temperature and high humidity conditions as specified in JOGIS07-2009 (treatment time: 48 hours). The haze amount (%) before and after the test was measured using a haze meter specified in JIS K7136:2000, and the difference in haze amount before and after the test, D, was calculated. H (%).

[0514] (3) Temperature coefficient of refractive index dn / dT

[0515] The temperature coefficient of refractive index dn / dT was determined for each optical glass by the following method.

[0516] A disc-shaped sample with a diameter of 20 mm and a thickness of 5 mm was prepared. Using a He-Ne gas laser, the temperature coefficient of the relative refractive index, dn / dT, at a wavelength of 632.8 nm was measured by interferometry in accordance with the Japan Optical Glass Manufacturers' Association standard JOGIS 18-2019, "Determination of the Temperature Coefficient of the Refractive Index of Optical Glass." Specifically, within the temperature range of -40°C to 150°C, the sample temperature was increased from -40°C to 140°C in 20°C increments and then from 140°C to 150°C in 10°C increments (heating rate: approximately 1°C / minute). The temperature coefficient of the refractive index, dn / dT, was determined for temperatures between 20°C and 40°C based on the results of continuous measurements of the sample temperature and the number of interference fringes.

[0517] All of the samples No. 1 to 45 shown in Tables 8 to 14 below were found to have a refractive index temperature coefficient dn / dT exceeding 0°C. -1 , which is a positive value.

[0518] The above results are shown in the following table. In the table, the unit of the content of the glass component is mass %. In the table, "○" means that the items described in the title of the column with "○" are met, and "×" means that the items described in the title of the column with "×" are not met. [Table 8-1]

[0519]

[0520] [Table 8-2]

[0521] [Table 8-3]

[0522]

[0523] [Table 9-1]

[0524]

[0525] [Table 9-2]

[0526]

[0527] [Table 9-3]

[0528]

[0529]

[0530]

[0531]

[0532]

[0533]

[0534]

[0535]

[0536]

[0537]

[0538]

[0539]

[0540]

[0541] [Table 14-1]

[0542]

[0543] [Table 14-2]

[0544]

[0545] [Table 14-3]

[0546]

[0547] [Example 3]

[0548] Using the various glasses obtained in Examples 1 and 2, glass blocks (glass gobs) for press molding were produced. These glass gobs were heated and softened in the atmosphere and then press-molded using a press molding mold to produce lens blanks (optical element blanks). The resulting lens blanks were removed from the press molding mold, annealed, and subjected to mechanical processing including polishing to produce spherical lenses made from the various glasses produced in Examples 1 and 2. Visual inspection of the resulting spherical lenses revealed no cracks or fissures.

[0549] [Example 4]

[0550] Desired amounts of the molten glass produced in Examples 1 and 2 were press-molded using a press-molding mold to produce lens blanks (optical element blanks). The resulting lens blanks were removed from the press-molding mold, annealed, and then machined, including polishing, to produce spherical lenses made from the various glasses produced in Examples 1 and 2. Visual inspection of the resulting spherical lenses revealed no cracks or fissures.

[0551] [Example 5]

[0552] The molten glasses produced in Examples 1 and 2 were solidified, and the glass blocks (optical element blanks) produced therefrom were annealed and subjected to machining including polishing to produce spherical lenses made of the various glasses produced in Examples 1 and 2.

[0553] It should be understood that the embodiments disclosed herein are all illustrative and not restrictive. The scope of the present invention is defined by the claims, not the foregoing description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0554] For example, by adjusting the composition of the glass composition exemplified above as described in the specification, the optical glass of one embodiment of the present invention can be obtained.

[0555] Furthermore, it is of course possible to arbitrarily combine two or more of the items exemplified or described as preferred ranges in the specification.

Claims

1. An optical glass, wherein: Based on quality standards, The B2O3 content is 3.00% or more and 70.00% or less, P2O5 content is 47.00% or more and 80.00% or less, Al2O3 content is less than 13.00%, Li2O content is above 0.01%, Na2O content is less than 5.00%, CaO content is less than 18.00%, The ZnO content is less than 23.00%, The total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is 66.00% or more and 84.00% or less, The total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 26.00% or less, wherein when the total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 15.00% or more and 26.00% or less, the total content of P2O5, B2O3 and SiO2 (P2O5+B2O3+SiO2) is 69.00% or more and 84.00% or less, The total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is less than 15.00%, The mass ratio of P2O5 content to B2O3 content (P2O5 / B2O3) is 18.00 or less, The mass ratio of the Na2O content to the total content of Li2O, Na2O and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.50 or less, The total content of MgO and CaO (MgO+CaO) is 2.00% or more, The mass ratio of the total content of Li2O and BaO to the content of B2O3 ((Li2O+BaO) / B2O3) is 0.59 or less, The mass ratio of the total content of Al2O3 and BaO to the content of Li2O ((Al2O3+BaO) / Li2O) is 2.77 or less, The mass ratio of the total content of MgO and CaO to the total content of Li2O, Na2O and K2O ((MgO+CaO) / (Li2O+Na2O+K2O)) is 6.10 or less, The mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of P2O5, B2O3 and SiO2 ((MgO+CaO+SrO+BaO+ZnO) / (P2O5+B2O3+SiO2)) is 0.36 or less, The optical glass has a refractive index nd of 1.70000 or less, an Abbe number νd of 60.00 or more, and an average linear expansion coefficient α at 100° C. to 300° C. of 130×10 -7 / K or less.

2. The optical glass according to claim 1, wherein The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 7.00% or less.

3. The optical glass according to claim 1, wherein: The Nb2O5 content is 5.00% or less.

4. The optical glass according to claim 1, wherein The total content of MgO, CaO, SrO, and BaO (MgO+CaO+SrO+BaO) is 4.90% or more and 26.00% or less.

5. The optical glass according to claim 1, wherein The mass ratio of the Na2O content to the total content of Li2O, Na2O, and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.19 or less.

6. The optical glass according to claim 1, wherein: The total content of ZnO and BaO (ZnO+BaO) is 20.50% or less.

7. The optical glass according to claim 1, wherein: The SiO2 content is less than 5.00%.

8. The optical glass according to claim 1, wherein: CaO content is less than 9.00%, or, The CaO content is 9.00% or more and 18.00% or less, and the total content of SrO and BaO (SrO+BaO) is less than 3.00%.

9. The optical glass according to claim 1, wherein: The total content of SrO and BaO (SrO+BaO) is 13.00% or less.

10. The optical glass according to claim 1, wherein: The total content of SrO, BaO and K2O (SrO+BaO+K2O) is 13.00% or less.

11. The optical glass according to claim 1, wherein: The mass ratio of the total content of SrO and BaO to the content of Li2O ((SrO+BaO) / Li2O) is 5.00 or less.

12. The optical glass according to claim 1, wherein: The P2O5 content is 47.00% or more and less than 58.00%, or, The P2O5 content is greater than 58.00% and less than 80.00% and the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li2O, Na2O and K2O ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+K2O)) is less than 6.

00.

13. The optical glass according to claim 1, which has a specific gravity of 3.00 g / cc or less. 14 . The optical glass according to claim 1 , wherein the external transmittance thereof at a wavelength of 400 nm to 700 nm is 60% or more when converted to a thickness of 10.0 mm.

15. The optical glass according to claim 1, wherein: The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is less than 7.00%, Nb2O5 content is less than 5.00%, The total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is 4.90% or more and 26.00% or less, The mass ratio of the Na2O content to the total content of Li2O, Na2O and K2O (Na2O / (Li2O+Na2O+K2O)) is 0.19 or less, The total content of ZnO and BaO (ZnO+BaO) is less than 20.50%, SiO2 content is less than 5.00%, The CaO content is less than 9.00% and the total content of SrO and BaO (SrO+BaO) is 13.00% or less, or the CaO content is 9.00% or more and 18.00% or less and the total content of SrO and BaO (SrO+BaO) is less than 3.00%, The total content of SrO, BaO and K2O (SrO+BaO+K2O) is less than 13.00%, The mass ratio of the total content of SrO and BaO to the content of Li2O ((SrO+BaO) / Li2O) is 5.00 or less, The P2O5 content is 47.00% or more and less than 58.00%, or the P2O5 content is 58.00% or more and 80.00% or less and the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li2O, Na2O and KO ((MgO+CaO+SrO+BaO+ZnO) / (Li2O+Na2O+KO)) is less than 6.00, The optical glass has a specific gravity of 3.00 g / cc or less and an external transmittance of 60% or more at a wavelength of 400 nm to 700 nm based on a thickness of 10.0 mm.

16. An optical glass, wherein: Based on quality standards, The SiO2 content is 0.00% or more and 5.00% or less, The B2O3 content is 0.00% or more and 20.00% or less, The P2O5 content is 60.00% or more, and when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more, The Al2O3 content is 1.00% or more and 30.00% or less, The K2O content is 0.00% or more and 5.00% or less, The MgO content is 0.00% or more and 10.00% or less, The CaO content is 0.00% or more and 15.00% or less, The SrO content is 0.00% or more and 5.00% or less, The BaO content is 0.00% or more and 5.00% or less, The ZnO content is 0.00% or more and 5.00% or less, The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is more than 71.00%, The total content of Li2O, Na2O and K2O (Li2O+Na2O+K2O) is 1.40% or more and 6.00% or less, The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00% or more and 4.00% or less, The optical glass has a refractive index nd of 1.49000 or greater, an Abbe number νd of 65.00 or greater, and an average linear expansion coefficient α (-30 / 70) of 90×10 -7 / K or less, and the difference in fogging amount before and after the weathering test is D H It is 0.0% or more and 5.0% or less.

17. The optical glass according to claim 16, wherein: The P2O5 content is 60.00% or more and 80.00% or less, wherein when the B2O3 content is 0.00% or more and 8.00% or less, the P2O5 content is 71.00% or more and 80.00% or less, Furthermore, the Al2O3 content is 1.00% or more and 14.00% or less.

18. The optical glass according to claim 16, wherein: Based on quality standards, The SiO2 content is 0.00% or more and 3.00% or less, The B2O3 content is 0.00% or more and 12.50% or less, wherein when the P2O5 content is 77.00% or more and the Al2O3 content is 14.00% or more and 30.00% or less, the B2O3 content is 4.75% or more and 12.50% or less, The Li2O content is 1.00% or more and 10.00% or less, The ZnO content is 0.00% or more and 3.50% or less, The CuO content is 0.00% or more and less than 0.50%, The B2O3 content is 3.00% or more and 20.00% or less, or the B2O3 content is 0.00% or more and less than 3.00% and the total content of MgO and CaO is 10.10% or more, The P2O5 content is 60.00% or more and less than 77.0%, or the P2O5 content is 77.00% or more and the Al2O3 content is 11.00% or more and 30.00% or less, Furthermore, the CaO content is 0.00% or more and less than 0.50%, or the CaO content is 0.50% or more and 15.00% or less and the Al2O3 content is 1.00% or more and less than 14.00%.

19. The optical glass according to claim 18, wherein: The total content of MgO and CaO (MgO+CaO) exceeds 3.00%, or, The total content of MgO and CaO (MgO+CaO) is 0.00% or more and 3.00% or less, and the Al2O3 content is 7.00% or more and 30.00% or less.

20. The optical glass according to claim 18, wherein The SiO2 content is 0.00% or more and 3.00% or less.

21. The optical glass according to claim 18, wherein: The Al2O3 content is 4.00% or more and 30.00% or less.

22. The optical glass according to claim 18, wherein: The Na2O content is 0.00% or more and 5.00% or less.

23. The optical glass according to claim 18, wherein: The K2O content is 0.00% or more and 2.50% or less.

24. The optical glass according to claim 18, wherein: The MgO content is 0.00% or more and 7.00% or less.

25. The optical glass according to claim 18, wherein: The ZnO content is 0.00% or more and 3.10% or less.

26. The optical glass according to claim 18, wherein: It contains virtually no PbO.

27. The optical glass according to claim 18, wherein: The total content of SiO2, B2O3, P2O5 and Al2O3 (SiO2+B2O3+P2O5+Al2O3) is 75.00% or more.

28. The optical glass according to claim 18, wherein: The mass ratio of the Al2O3 content to the P2O5 content (Al2O3 / P2O5) is 0.20 or less.

29. The optical glass according to claim 18, wherein: The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) is 0.00%. or, The total content of La2O3, Y2O3 and Gd2O3 (La2O3+Y2O3+Gd2O3) exceeds 0.000% and is 4.00% or less, and the total content of P2O5 and B2O3 (P2O5+B2O3) exceeds 80.00%.

30. The optical glass according to claim 18, wherein: The Sb2O3 content is 0.01 mass % or more as an added ratio.

31. The optical glass according to claim 18, wherein: The Al2O3 content is 14.00% or more and the mass ratio of the Li2O content to the Al2O3 content (Li2O / Al2O3) is 0.13 or less.

32. An optical element made of the optical glass according to any one of claims 1 to 31.

Images