Optical glass and optical element

Abstract

The invention provides optical glass which can achieve target parameters in a stable and devitrification-free manner while reducing the cost, and an optical element comprising the optical glass. In the glass composition of the optical glass expressed by mass%, the content of SiO2 is 0-20%, the content of B2O3 is 5-30%, the content of BaO is 0-6.5%, the content of La2O3 is 29-55%, the content of TiO2 is 5-50%, the content of Nb2O5 is 0-5%, the content of WO3 is 0-0.6%, the content of CaO is less than 15%, the content of ZnO is 0-20%, the content of ZrO2 is 0-20%, and the mass ratio of the total content of TiO2 and ZrO2 to the content of CaO ((TiO2 + ZrO2) / CaO) is greater than 3.3.

Description

Technical Field

[0001] This invention relates to optical glass that achieves stable, non-de-transmitting optical parameters while reducing costs, and optical elements incorporating the optical glass. Background Technology

[0002] In the composition of optical glass, niobium oxide (Nb2O5) can increase the refractive index, reduce the Abbe number, and improve the glass's resistance to devitrification. However, excessive amounts of niobium oxide can reduce the glass's resistance to devitrification, decrease visible light transmittance, and increase the glass's specific gravity and cost.

[0003] Patent document 1 discloses an optical glass containing Nb2O5, but its Nb2O5 content is relatively high.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Chinese Patent Application Publication No. 111320384 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Therefore, the present invention was developed in view of the above-mentioned problems, and its object is to provide an optical glass that achieves stable, non-de-transmitting optical parameters while reducing costs, as well as an optical element comprising the optical glass. In particular, a low-cost, high-refractive-index, low-specific-gravity optical glass is provided.

[0009] Problem Solving Methods

[0010] The main points of this invention are as follows.

[0011] (1) An optical glass, wherein, in the glass composition of the optical glass expressed as % by mass,

[0012] The SiO2 content is 0-20%.

[0013] The B2O3 content is 5%–30%.

[0014] The BaO content is 0-6.5%.

[0015] The La2O3 content is 29-55%.

[0016] The TiO2 content is 5-50%.

[0017] The Nb2O5 content is 0-5%.

[0018] The WO3 content is 0-0.6%.

[0019] The CaO content is below 15%.

[0020] The ZnO content is 0-20%.

[0021] The ZrO2 content is 0-20%.

[0022] The total content of TiO2 and ZrO2 relative to the mass ratio of CaO content ((TiO2+ZrO2) / CaO) is greater than 3.3.

[0023] (2) The optical glass according to (1), wherein, in mass percent, at least one of the following is satisfied:

[0024] The Y2O3 content is below 4.31%.

[0025] The Na2O content is below 1.16%.

[0026] The Gd2O3 content is less than 3%.

[0027] The Ta2O5 content is less than 3%.

[0028] (3) The optical glass according to (1) or (2), wherein,

[0029] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is greater than 0.

[0030] (4) The optical glass according to any one of (1) to (3), wherein,

[0031] The mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is greater than 0.85.

[0032] (5) The optical glass according to any one of (1) to (4), wherein,

[0033] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.5 to 5.87.

[0034] (6) The optical glass according to any one of (1) to (5), wherein the total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 29-55%.

[0035] (7) The optical glass according to any one of (1) to (6), wherein,

[0036] The mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is greater than 0 and less than 6.1.

[0037] (8) The optical glass according to any one of (1) to (7), wherein,

[0038] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.24.

[0039] (9) The optical glass according to any one of (1) to (8), wherein,

[0040] The mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0 to 0.35.

[0041] (10) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0042] The Nb2O5 content is 0-4%;

[0043] The SiO2 content is 1-18%;

[0044] The B2O3 content is 7-28%;

[0045] The BaO content is 0–5.5%;

[0046] The ZnO content is 1-18%;

[0047] The La2O3 content is 31-53%;

[0048] The Y2O3 content is less than 3%;

[0049] The TiO2 content is 7-45%;

[0050] The WO3 content is 0-0.5%;

[0051] The ZrO2 content is 1-19%;

[0052] The CaO content is 1-13%;

[0053] The Na2O content is below 0.8%;

[0054] The Gd2O3 content is less than 2%;

[0055] The Ta2O5 content is less than 2%;

[0056] The total content of TiO2 and ZrO2 relative to the mass ratio of CaO content ((TiO2+ZrO2) / CaO) is greater than 3.35;

[0057] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.05 to 1.0.

[0058] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.6 to 5.5;

[0059] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 33-55%;

[0060] The mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is 0.4 to 5.7;

[0061] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.2;

[0062] The mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is 0.9 or higher;

[0063] The mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0 to 0.3;

[0064] The refractive index nd is 1.8800–1.9200;

[0065] The Abbe number vd is 28–33;

[0066] Specific gravity is 4.00–5.00;

[0067] The glass transition temperature (Tg) is 600–670℃.

[0068] λ 70 The wavelength is 375–440 nm.

[0069] λ5 is 350–370 nm.

[0070] (11) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0071] The Nb2O5 content is 0-3%;

[0072] The SiO2 content is 2-16%;

[0073] The B2O3 content is 9-26%;

[0074] The BaO content is 0.1%–4.5%;

[0075] The ZnO content is 2-16%;

[0076] The La2O3 content is 33-51%;

[0077] The Y2O3 content is less than 2%;

[0078] The TiO2 content is 9-40%;

[0079] The WO3 content is 0-0.4%;

[0080] The ZrO2 content is 2-18%;

[0081] The CaO content is 2-12%;

[0082] The Na2O content is below 0.4%;

[0083] The Gd2O3 content is less than 1%;

[0084] The Ta2O5 content is less than 1%;

[0085] The total content of TiO2 and ZrO2 relative to the content of CaO ((TiO2+ZrO2) / CaO) is greater than 3.40;

[0086] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.10 to 0.8.

[0087] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.7 to 5.0;

[0088] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 36.4% to 55%;

[0089] The mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is 0.8–4.9;

[0090] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.15;

[0091] The mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is 0.95 or higher;

[0092] The mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0 to 0.2;

[0093] The refractive index nd is 1.8850–1.9180;

[0094] The Abbe number vd is 28.5–32.6;

[0095] Specific gravity is 4.05–4.90;

[0096] The glass transition temperature (Tg) is 604–668 °C.

[0097] λ 70 The wavelength range is 376–439 nm.

[0098] λ5 is 352–368 nm.

[0099] (12) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0100] The Nb₂O₅ content is 0–2%.

[0101] The SiO2 content is 3-12%;

[0102] The B2O3 content is 11-24%;

[0103] The BaO content is 0.1%–3.5%;

[0104] The ZnO content is 3-15%;

[0105] The La2O3 content is 35-49%;

[0106] The Y2O3 content is less than 1%;

[0107] The TiO2 content is 11-30%;

[0108] The WO3 content is 0-0.3%;

[0109] The ZrO2 content is 3-17%;

[0110] The CaO content is 2.5%–11%;

[0111] The Na2O content is 0%;

[0112] The Gd2O3 content is 0%;

[0113] The Ta2O5 content is 0%;

[0114] The total content of TiO2 and ZrO2 relative to the content of CaO ((TiO2+ZrO2) / CaO) is greater than 3.45;

[0115] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.15 to 0.7.

[0116] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.8 to 4.5;

[0117] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 37-51%;

[0118] The mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is 1.2 to 4.1;

[0119] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.1;

[0120] The mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is greater than 1.00;

[0121] The mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0 to 0.1;

[0122] The refractive index nd is 1.8900–1.9160;

[0123] The Abbe number vd is 29–32.2;

[0124] Specific gravity is 4.10–4.85;

[0125] The glass transition temperature (Tg) is 606–666 °C.

[0126] λ 70 The wavelength range is 378–438 nm.

[0127] λ5 is 354–367 nm.

[0128] (13) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0129] The Nb₂O₅ content is 0–1%;

[0130] The SiO2 content is 4-10%;

[0131] The B2O3 content is 12-22%;

[0132] The BaO content is 0.2%–2.5%;

[0133] The La2O3 content is 37-47%;

[0134] The Y2O3 content is 0%;

[0135] The TiO2 content is 12-20%;

[0136] The WO3 content is 0-0.2%;

[0137] The ZrO2 content is 4-16%;

[0138] The CaO content is 3-10%;

[0139] The total content of TiO2 and ZrO2 relative to the content of CaO ((TiO2+ZrO2) / CaO) is greater than 3.50;

[0140] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.20 to 0.60;

[0141] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.9 to 4.0;

[0142] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 38-49%;

[0143] The mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is 1.6 to 3.3;

[0144] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.05;

[0145] The mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is greater than 1.10;

[0146] The mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0;

[0147] The refractive index nd is 1.8950–1.9120;

[0148] The Abbe number vd is 30–31.8;

[0149] Specific gravity is 4.15–4.80;

[0150] The glass transition temperature (Tg) is 610–664 °C.

[0151] λ70 The wavelength range is 379–437 nm.

[0152] λ5 is 355–366 nm.

[0153] (14) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0154] The Nb2O5 content is 0%;

[0155] The B2O3 content is 13-20%;

[0156] The BaO content is 0.2%–1.5%;

[0157] The La2O3 content is 39-45%;

[0158] The WO3 content is 0-0.1%;

[0159] The ZrO2 content is 5-15%;

[0160] The total content of TiO2 and ZrO2 relative to the mass ratio of CaO content ((TiO2+ZrO2) / CaO) is greater than 3.55;

[0161] The mass ratio of CaO content to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.20 to 0.50;

[0162] The mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 2.0 to 3.5;

[0163] The total content of La2O3, Gd2O3 and Y2O3 (La2O3+Gd2O3+Y2O3) is 39-45%;

[0164] The mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3 and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0;

[0165] The refractive index nd is 1.9000–1.9100;

[0166] The Abbe number vd is 31–31.6;

[0167] Specific gravity is 4.20–4.70;

[0168] λ 70 The wavelength range is 380–436 nm.

[0169] λ5 is 356–365 nm.

[0170] (15) The optical glass according to any one of (1) to (9) satisfies at least one of the following:

[0171] The BaO content is 0.3-0.5%;

[0172] The WO3 content is 0%.

[0173] (16) An optical element comprising the optical glass described in any one of (1) to (15).

[0174] The effects of the invention

[0175] According to the present invention, an optical glass that achieves stable, non-de-transmitting optical parameters while reducing costs can be provided, as well as an optical element comprising the optical glass. Detailed Implementation

[0176] The embodiments of the present invention will be described below. It should be noted that, unless otherwise specified, the glass composition of the optical glass in this invention and this specification is expressed on an oxide basis. Here, "oxide-based glass composition" refers to the glass composition obtained by converting substances that exist in the optical glass in the form of oxides after the glass raw material has completely decomposed during melting. Each glass component is conventionally described as SiO2, TiO2, etc. Unless otherwise specified, the content and total content of the glass components are on a mass basis, and "%" refers to "mass %".

[0177] The content of the glass components can be quantified using known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, in this specification and this invention, a content of 0% for a constituent component means that the component is substantially absent, allowing for the presence of the component at an unavoidable impurity level.

[0178] In addition, unless otherwise specified, the refractive index in this specification refers to the refractive index nd under helium d rays (wavelength 587.56 nm).

[0179] The glass composition of the optical glass of the present invention will be described in more detail below.

[0180] (Glass composition)

[0181] In the optical glass of the present invention, the SiO2 content is 0-20%. The lower limit of the SiO2 content is preferably 1%, and more preferably 2%, 3%, and 4% in the following order. Furthermore, the upper limit of the SiO2 content is preferably 18%, and more preferably 17%, 16%, 15%, 14%, 13%, 12%, 11%, and 10% in the following order. SiO2 is a network-forming component of the glass. Adding SiO2 can increase the viscosity of the molten glass, improve the glass's resistance to devitrification, suppress the rise in the glass transition temperature, and reduce the glass's specific gravity. However, excessive SiO2 content will cause a decrease in the refractive index.

[0182] In the optical glass of the present invention, the content of B2O3 is 5% to 30%. The lower limit of the B2O3 content is preferably 6%, and more preferably 7%, 8%, 9%, 10%, 11%, 12%, and 13% in the following order. Furthermore, the upper limit of the B2O3 content is preferably 29%, and more preferably 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, and 20% in the following order. B2O3 is a network-forming component of glass and is an indispensable component as a glass-forming oxide. The B2O3 content can improve the glass's resistance to devitrification and reduce its specific gravity. However, when the B2O3 content is too high, the refractive index of the glass decreases, the Abbe number increases, and chemical durability decreases.

[0183] In the optical glass of the present invention, the Nb2O5 content is 0 to 5%. The Nb2O5 content is preferably 4% or less, more preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and even more preferably 0%. The Nb2O5 content can increase the refractive index, reduce the Abbe number, and improve the glass's devitrification properties. However, excessive Nb2O5 content will reduce the glass's devitrification resistance, decrease visible light transmittance, increase the glass's specific gravity, and increase the cost of the glass material.

[0184] In the optical glass of the present invention, the BaO content is 0 to 6.5%. The lower limit of the BaO content is preferably 0.1%, and more preferably 0.2% and 0.3% in the following order. Furthermore, the upper limit of the BaO content is preferably 6%, and more preferably 5.5%, 5.0%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, and 0.5% in the following order. The BaO content can increase the refractive index of the glass, improve the melt flowability and devitrification resistance of the glass raw material, and lower the glass transition temperature. However, excessive BaO content can cause devitrification and an increase in specific gravity in the glass.

[0185] In the optical glass of the present invention, the La2O3 content is 29-55%. The lower limit of the La2O3 content is preferably 30%, and more preferably 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, and 39% in the following order. Furthermore, the upper limit of the La2O3 content is preferably 54%, and more preferably 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, and 45% in the following order. As a rare earth oxide, La2O3 can increase the refractive index and suppress the increase of the Abbe number. However, excessive La2O3 content can reduce the stability of the glass and raise concerns about increased devitrification.

[0186] In the optical glass of the present invention, the TiO2 content is 5% to 50%. The lower limit of the TiO2 content is preferably 6%, and more preferably 7%, 8%, 9%, 10%, 11%, and 12% in the following order. Furthermore, the upper limit of the TiO2 content is preferably 50%, and more preferably 45%, 40%, 35%, 30%, 25%, and 20% in the following order. The TiO2 content can increase the refractive index of the glass, reduce the Abbe number, and improve the devitrification of the glass. However, excessive TiO2 content increases the coloration of the glass, reduces the visible light transmittance, decreases the Abbe number, and increases the risk of devitrification.

[0187] In the optical glass of the present invention, the WO3 content is 0 to 0.6%. The WO3 content is preferably 0.5% or less, more preferably 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, and even more preferably 0%. WO3 is a component that increases the refractive index and dispersion of glass; adding WO3 also tends to reduce glass crystallinity. However, excessive WO3 content increases the coloration of the glass, reduces its light transmittance, and increases its specific gravity.

[0188] Furthermore, the contents of glass components other than those described above in the optical glass of the present invention are shown in non-limiting examples below.

[0189] In the optical glass of the present invention, the CaO content is 15% or less. The lower limit of the CaO content is preferably 0.5%, and more preferably 1%, 1.5%, 2%, 2.5%, and 3% in the following order. Furthermore, the upper limit of the CaO content is preferably 14%, and more preferably 13%, 12%, 11%, and 10% in the following order. CaO is a component that improves the meltability of glass raw materials and reduces the specific gravity of the glass. However, excessive CaO content will cause a decrease in the refractive index of the glass and increase the risk of devitrification.

[0190] In the optical glass of the present invention, the ZnO content is 0-20%. The lower limit of the ZnO content is preferably 0.5%, and more preferably 1%, 1.5%, 2%, 2.5%, and 3% in the following order. Furthermore, the upper limit of the ZnO content is preferably 19%, and more preferably 18%, 17%, 16%, and 15% in the following order. ZnO is a component that lowers the glass transition temperature, reduces the specific gravity, and improves the chemical stability of the glass. However, excessive ZnO content can lead to a decrease in the glass's refractive index, a decrease in the glass's melt viscosity, and an increased risk of devitrification.

[0191] In the optical glass of the present invention, the Y2O3 content is 4.31% or less. The Y2O3 content is preferably 4% or less, more preferably 3% or less, 2% or less, 1% or less, 0.5% or less, and even more preferably 0%. Y2O3 is a component that improves the refractive index of the glass, reduces dispersion, and improves the weather resistance of the glass. However, when the Y2O3 content is too high, it is difficult to achieve the required dispersion reduction for the glass, and the glass is prone to devitrification.

[0192] In the optical glass of the present invention, the ZrO2 content is 0-20%. The lower limit of the ZrO2 content is preferably 0.5%, and more preferably 1%, 1.5%, 2%, 3%, 4%, and 5% in the following order. Furthermore, the upper limit of the ZrO2 content is preferably 19%, and more preferably 18%, 17%, 16%, and 15% in the following order. ZrO2 is a component that improves the refractive index and weather resistance of the glass. However, excessive ZrO2 content will cause an increase in the Abbe number of the glass and a decrease in its devitrification resistance.

[0193] In the optical glass of the present invention, the content of Na2O is 1.16% or less. The content of Y2O3 is preferably 1.0% or less, more preferably 0.8% or less, 0.4% or less, 0.2% or less, and even more preferably 0% in the following order. Na2O is a component that improves the meltability of glass raw materials, but excessive Na2O content will cause devitrification of the glass.

[0194] In the optical glass of the present invention, the Gd2O3 content is 3% or less. The Gd2O3 content is preferably 2.5% or less, more preferably 2.0% or less, 1.5% or less, 1.0% or less, 0.5% or less, and even more preferably 0%. Gd2O3 is a component that improves the refractive index and devitrification resistance of glass, but excessive Gd2O3 content can cause glass devitrification, increase the glass's specific gravity, and increase the cost of the glass.

[0195] In the optical glass of the present invention, the Ta2O5 content is 3% or less. The Ta2O5 content is preferably 2.5% or less, more preferably 2.0% or less, 1.5% or less, 1.0% or less, 0.5% or less, and even more preferably 0%. Ta2O5 is a component that increases the refractive index of the glass, improves its resistance to devitrification, and increases the viscosity of the molten glass. However, excessively high Ta2O5 content increases the specific gravity of the glass and also increases the cost of the glass.

[0196] Furthermore, in the optical glass of the present invention, the mass ratio of the total content of TiO2 and ZrO2 to the content of CaO ((TiO2+ZrO2) / CaO) is greater than 3.3. This mass ratio ((TiO2+ZrO2) / CaO) is preferably 3.35 or more, and more preferably 3.40 or more, 3.45 or more, 3.50 or more, and 3.55 or more in the following order. By setting this mass ratio ((TiO2+ZrO2) / CaO) within the above range, the desired glass specific gravity and light transmittance can be obtained, achieving the optical parameters that are the objectives of the present invention.

[0197] In the optical glass of the present invention, the mass ratio of CaO content to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is greater than 0. The lower limit of this mass ratio (CaO / (CaO+BaO+SrO+ZnO)) is preferably 0.05, and more preferably 0.1, 0.15, and 0.20 in the following order. Furthermore, the upper limit of this mass ratio (CaO / (CaO+BaO+SrO+ZnO)) is preferably 1.0, and more preferably 0.90, 0.80, 0.70, 0.60, and 0.50 in the following order. By setting this mass ratio (CaO / (CaO+BaO+SrO+ZnO)) within the above range, a desired glass specific gravity can be obtained while improving the light transmittance of the glass.

[0198] In the optical glass of the present invention, the mass ratio of TiO2 content to ZnO content (TiO2 / ZnO) is greater than 0.85. This mass ratio (TiO2 / ZnO) is preferably 0.90 or higher, and more preferably 0.95 or higher, 1.00 or higher, 1.05 or higher, and 1.10 or higher in the following order. By setting this mass ratio (TiO2 / ZnO) within the above range, the desired glass specific gravity and light transmittance can be obtained, achieving the optical parameters objective of the present invention. ZnO can lower the glass liquidus temperature and improve the glass's resistance to devitrification. The TiO2 / ZnO ratio can reflect changes in the glass liquidus temperature, but if this ratio is too high, the glass liquidus temperature increases, which is detrimental to achieving the target parameters; if this ratio is too low, the glass viscosity decreases, which is detrimental to glass forming.

[0199] In the optical glass of the present invention, the mass ratio of B2O3 content to SiO2 content (B2O3 / SiO2) is 1.5 to 5.87. The lower limit of this mass ratio (B2O3 / SiO2) is preferably 1.6, and more preferably 1.7, 1.8, 1.9, and 2.0 in the following order. Furthermore, the upper limit of this mass ratio (B2O3 / SiO2) is preferably 5.5, and more preferably 5.0, 4.5, 4.0, and 3.5 in the following order. If the mass ratio (B2O3 / SiO2) is too high, the viscosity of the glass decreases, which is detrimental to glass forming. Conversely, if the mass ratio (B2O3 / SiO2) is too low, the viscosity of the glass increases, which is also detrimental to glass forming.

[0200] In the optical glass of the present invention, the total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) is 29-55%, preferably 36.4-55%. The lower limit of this total content (La2O3+Gd2O3+Y2O3) is preferably 31%, and more preferably 32%, 33%, 34%, 25%, 36%, 37%, 38%, and 39% in the following order. Furthermore, the upper limit of this total content (La2O3+Gd2O3+Y2O3) is preferably 54%, and more preferably 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, and 45% in the following order. By setting the total content (La2O3+Gd2O3+Y2O3) within the above range, the refractive index of the glass can be increased, the dispersion of the glass can be reduced, and the increase in the melting temperature of the glass, the decrease in the stability of the glass, and the decrease in the resistance to devitrification can be avoided.

[0201] In the optical glass of the present invention, the mass ratio of B2O3 content to ZrO2 content (B2O3 / ZrO2) is greater than 0 and less than 6.1. The lower limit of this mass ratio (B2O3 / ZrO2) is preferably 0.4, and more preferably 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6 in the following order. Furthermore, the upper limit of this mass ratio (B2O3 / ZrO2) is preferably 5.7, and more preferably 5.3, 4.9, 4.5, 4.1, 3.7, and 3.3 in the following order. By setting this mass ratio (B2O3 / ZrO2) within the above range, the weather resistance and stability of the glass can be improved, the viscosity can be kept within a suitable range, and the network structure of the glass is not damaged, nor is the crystallization temperature of the glass increased.

[0202] In the optical glass of the present invention, the mass ratio of Nb2O5 content to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.24. This mass ratio (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is preferably 0.20 or less, more preferably 0.15 or less, 0.10 or less, 0.05 or less, and more preferably 0. By setting this mass ratio (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) within the above range, a higher refractive index and a lower Abbe number can be obtained while achieving a desired glass specific gravity.

[0203] In the optical glass of the present invention, the mass ratio of Y2O3 content to B2O3 content (Y2O3 / B2O3) is 0 to 0.35. This mass ratio (Y2O3 / B2O3) is preferably 0.30 or less, more preferably 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, 0.05 or less, and even more preferably 0. Y2O3 is a high refractive index component, and B2O3 is a low refractive index component. This ratio can reflect changes in the glass's refractive index and stability; however, if this ratio is too high, the glass's stability decreases.

[0204] Furthermore, the glass of the present invention may also contain Sb₂O₃ and ZnS components as needed. Sb₂O₃ has an antifoaming effect during molten glass production, while ZnS, added to the glass raw material as a reducing agent, can inhibit platinum from contaminating the glass and improve its transmittance. The content of ZnS as a reducing agent relative to the total mass of the glass can be less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%, and the content of Sb₂O₃ as an antifoaming agent relative to the total mass of the glass can be less than 3% or less, or less than 2%.

[0205] (Glass properties)

[0206] <Refractive index nd>

[0207] The refractive index nd of the optical glass of the present invention is preferably 1.8800 to 1.9200. The lower limit of the refractive index nd is preferably 1.8850, and more preferably 1.8900, 1.8950, and 1.9000 in the following order. In addition, the upper limit of the refractive index nd is preferably 1.9180, and more preferably 1.9160, 1.9140, 1.9120, and 1.9100 in the following order.

[0208] The refractive index nd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively increase the refractive index nd (high refractive index components) include TiO2, ZrO2, La2O3, Y2O3, and Gd2O3. On the other hand, components that relatively decrease the refractive index nd (low refractive index components) include SiO2, B2O3, and Na2O. Furthermore, the refractive index nd can also be adjusted to a desired value by appropriately adjusting the aforementioned content ratios.

[0209] <Abbe Numbers vd>

[0210] The Abbe number νd is a value representing properties related to dispersion, expressed using the refractive indices nd, nF, and nC of the d-line, F-line, and C-line as νd = (nd - 1) / (nF - nC). In the optical glass of the present invention, the Abbe number vd is preferably 28 to 33. The lower limit of the Abbe number vd is preferably 28.5, and more preferably 29.0, 29.5, 30.0, 30.5, and 31.0 in the following order. Furthermore, the upper limit of the Abbe number vd is preferably 32.6, and more preferably 32.2, 32.0, 31.8, and 31.6 in the following order.

[0211] The Abbe number vd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively decrease the Abbe number vd include La2O3 and Nb2O5. On the other hand, components that relatively increase the Abbe number vd include B2O3. Furthermore, the Abbe number vd can also be adjusted to a desired value by appropriately adjusting the aforementioned content ratios.

[0212] <Specific gravity of glass>

[0213] The specific gravity of the optical glass of the present invention is preferably 4.00 to 5.00. The lower limit of the specific gravity of the optical glass is preferably 4.05, and more preferably 4.10, 4.15, and 4.20 in the following order. In addition, the upper limit of the specific gravity is preferably 4.90, and more preferably 4.85, 4.80, 4.75, and 4.70 in the following order.

[0214] The specific gravity of the glass can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively increase the specific gravity include BaO, La2O3, ZrO2, Nb2O5, and Ta2O5. On the other hand, components that relatively decrease the specific gravity include SiO2, B2O3, Li2O, Na2O, and K2O. Alternatively, the specific gravity of the glass can also be adjusted to a desired value by appropriately adjusting the aforementioned content ratios.

[0215] <Glass transition temperature Tg>

[0216] The glass transition temperature (Tg) of the optical glass of the present invention is preferably 600–670°C. The lower limit of the glass transition temperature (Tg) is preferably 602°C, and more preferably 604°C, 606°C, 608°C, and 610°C in the following order. Furthermore, the upper limit of the glass transition temperature (Tg) is preferably 669°C, and more preferably 668°C, 667°C, 666°C, 665°C, 664°C, 663°C, and 662°C in the following order.

[0217] The glass transition temperature (Tg) can be adjusted to a desired value by changing the content of each glass component. Components that relatively lower the glass transition temperature (Tg) include BaO, ZnO, and Na₂O. Components that relatively increase the glass transition temperature (Tg) include La₂O₃, ZrO₂, and Nb₂O₅. Alternatively, the glass transition temperature (Tg) can also be adjusted to a desired value by appropriately changing the aforementioned content ratios.

[0218] <Light Transmittance of Glass>

[0219] The light transmittance of the optical glass of this invention can be determined by its tinting degree λ. 70 And λ5 are used for evaluation.

[0220] For a glass sample with a thickness of 10.0 mm ± 0.1 mm, the spectroscopic transmittance in the wavelength range of 200–700 nm was measured. The wavelength at which the external transmittance is 70% was defined as λ. 70 Let the wavelength with an external transmittance of 5% be set as λ5.

[0221] The λ of the optical glass of the present invention 70 Preferably, the wavelength is 375–440 nm. 70 The lower limit is preferably 376nm, and more preferably 377nm, 378nm, 379nm, and 380nm in the following order. 70 The upper limit is preferably 439nm, and more preferably 438nm, 437nm, and 436nm in the following order.

[0222] The λ5 of the optical glass of the present invention is preferably 350-370 nm. The lower limit of λ5 is preferably 351 nm, and more preferably 352 nm, 353 nm, 354 nm, 355 nm, and 356 nm in the following order. The upper limit of λ5 is preferably 369 nm, and more preferably 368 nm, 367 nm, 366 nm, and 365 nm in the following order.

[0223] It should be noted that the λ of the optical glass of this invention 70 The desired range of λ5 can be achieved by adjusting the content of each glass component, as well as the sum or ratio of the aforementioned contents.

[0224] (Manufacturing of optical glass)

[0225] The glass of the present invention is prepared by blending glass raw materials to achieve the given composition, and can be manufactured using the blended glass raw materials according to known glass manufacturing methods. For example, multiple compounds are blended and thoroughly mixed to prepare a batch of raw materials, which are then placed in a quartz crucible or a platinum crucible for rough melting. The molten material obtained from the rough melting is quenched and pulverized to produce crushed glass. The crushed glass is further placed in a platinum crucible for heating and remelting to produce molten glass. After further clarification and homogenization, the molten glass is shaped and slowly cooled to obtain optical glass. The shaping and slow cooling of the molten glass can be performed using known methods.

[0226] It should be noted that as long as the desired glass composition can be introduced into the glass and the desired content can be achieved, there are no particular restrictions on the compounds used when preparing batch raw materials. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, and fluorides.

[0227] (Manufacturing of optical components, etc.)

[0228] When manufacturing optical elements using the optical glass of the present invention, known methods can be employed. For example, in the manufacturing of the aforementioned optical glass, molten glass is injected into a mold to form a plate, thus producing a glass material formed from the optical glass of the present invention. The obtained glass material is appropriately cut, ground, and polished to produce fragments of a suitable size and shape for pressing. The fragments are heated and softened, and then pressed (re-hot-pressed) using known methods to produce an optical element blank with a shape approximating that of an optical element. The optical element blank is annealed, and then ground and polished using known methods to manufacture the optical element.

[0229] Depending on the intended use, anti-reflective films, total reflection films, etc., can be applied to the optical functional areas of the manufactured optical components.

[0230] According to one aspect of the present invention, an optical element formed from the aforementioned optical glass can be provided. Examples of optical elements include spherical lenses, aspherical lenses, lenses, prisms, diffraction gratings, etc. Examples of lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, concave meniscus lenses, and so on. The optical element can be manufactured by a method including processing a glass molded body formed from the aforementioned optical glass. Examples of processing include cutting, shaving, rough grinding, fine grinding, and polishing. When such processing is performed, by using the aforementioned glass, breakage can be reduced, and high-quality optical elements can be consistently provided.

[0231] Example

[0232] The present invention will now be described in more detail through embodiments. However, the present invention is not limited to the embodiments shown.

[0233] Glass samples with the glass compositions shown in Tables 1 to 5 were prepared in the following order, and various evaluations were performed.

[0234] Manufacturing of optical glass

[0235] First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass are prepared as raw materials. The raw materials are weighed and mixed thoroughly to achieve the glass composition shown in Tables 1 to 5. The resulting mixed raw materials (batch raw materials) are then placed in a platinum crucible and heated at 1350°C to 1400°C for 2 to 4 hours to produce molten glass. The mixture is stirred to homogenize the glass. After clarification, the molten glass is cast into a mold preheated to an appropriate temperature. The cast glass is then heat-treated at any temperature between Tg and 100°C lower than the glass transition temperature Tg for 30 minutes, and then naturally cooled to room temperature in a furnace to obtain a glass sample.

[0236] [Confirmation of glass composition]

[0237] The contents of each glass component were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) for the obtained glass samples, and the contents were confirmed to be consistent with those shown in Tables 1 to 5.

[0238] [Determination of optical properties]

[0239] The obtained glass samples were further annealed near the glass transition temperature (Tg) for approximately 30 minutes to 2 hours, and then cooled to room temperature in a furnace at a cooling rate of -30°C / hour to obtain annealed samples. The refractive index, Abbe number νd, specific gravity, glass transition temperature (Tg), and λ of the annealed samples were measured. 70 And λ5, the results are shown in Tables 1 to 5 respectively.

[0240] (i) Refractive index and Abbe number νd

[0241] For the annealed samples mentioned above, the refractive index at the 12 wavelengths shown in Table A was measured using the Japanese Industrial Standard (JIS) B 7071-1 Method for Determining the Refractive Index of Optical Glass - Part 1: Minimum Deflection Angle Method.

[0242] Next, the refractive indices of each ray obtained through measurement are substituted into the Schott dispersion formula specified in Appendix B of the Japanese Industrial Standard (JIS) JIS B7071-1 Method for Determination of Refractive Index of Optical Glass - Part 1: Method of Minimum Deflection Angle, and the constant of the Schott dispersion formula is obtained by least squares method. Then, using the Schott dispersion formula with determined constant, the Abbe number νd is calculated.

[0243] (ii) Specific gravity

[0244] Specific gravity was determined by the Archimedes method.

[0245] (iii) Glass transition temperature Tg

[0246] The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10 °C / min.

[0247] (iv)λ 70 λ5

[0248] The annealed sample was processed into a 10 mm thick, optically polished plane with parallel surfaces. The spectral transmittance in the wavelength range of 280 nm to 700 nm was measured. The intensity of light incident perpendicularly to one of the optically polished planes was defined as intensity A, and the intensity of light exiting from the other plane was defined as intensity B. The spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance is 70% was defined as λ. 70 The wavelength with a spectral transmittance of 5% is set as λ5. It should be noted that the spectral transmittance also includes the light reflection loss from the sample surface.

[0249]

[0250]

[0251]

[0252]

[0253]

[0254] According to Tables 1 to 5 above, the present invention can achieve stable, non-de-transmitting optical glass that meets the target parameters while reducing costs. In particular, it can provide high-refractive-index, low-density optical glass at low cost.

[0255] It should be understood that all the embodiments disclosed herein are exemplary and do not constitute a limitation. The scope of the invention is defined by the claims, not the foregoing description, and is intended to include all modifications within the meaning and scope of the claims.

[0256] For example, by adjusting the glass composition described in the specification as shown in the example above, an optical glass according to one embodiment of the present invention can be manufactured.

[0257] In addition, of course, any combination of two or more items exemplified in the specification or described as preferred items can be made.

Claims

1. An optical glass, in a glass composition of the optical glass expressed in mass%, Si02 content is 0 to 20%, B203 content is 5 to 30%, BaO content is 0 to 6.5%, La203 content is 29 to 55%, Ti02 content is 5 to 50%, Nb205 content is 0 to 5%, WO3 content is 0 to 0.6%, CaO content is 15% or less, ZnO content is 0 to 20%, Zr02 content is 0 to 20%, mass ratio of the total content of Ti02 and Zr02 with respect to CaO content ((Ti02+Zr02) / CaO) is more than 3.

3. satisfies at least one of the following in mass%:

2. The optical glass according to claim 1, wherein Y203 content is 4.31% or less, Na20 content is 1.16% or less, Gd203 content is 3% or less, Ta205 content is 3% or less.

3. The optical glass according to claim 1 or 2, wherein, mass ratio of CaO content with respect to the total content of CaO, BaO, SrO and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is more than 0.

4. The optical glass according to any one of claims 1 to 3, wherein, mass ratio of Ti02 content with respect to ZnO content (Ti02 / ZnO) is more than 0.

85.

5. The optical glass according to any one of claims 1 to 4, wherein, mass ratio of B203 content with respect to Si02 content (B203 / Si02) is 1.5 to 5.

87. total content of La203, Gd203 and Y203 (La203+Gd203+Y203) is 29 to 55%.

6. The optical glass according to any one of claims 1 to 5, wherein 7. The optical glass according to any one of claims 1 to 6, wherein, mass ratio of B203 content with respect to Zr02 content (B203 / Zr02) is more than 0 and 6.1 or less.

8. The optical glass according to any one of claims 1 to 7, wherein, mass ratio of Nb205 content with respect to the total content of Nb205, Ti02, W03 and Ta205 (Nb205 / (Nb205+Ti02+WO3+Ta205)) is 0 to 0.

24.

9. The optical glass according to any one of claims 1 to 8, wherein, mass ratio of Y203 content with respect to B203 content (Y203 / B203) is 0 to 0.

35.

10. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: Nb205 content is 0 to 4%, Si02 content is 1 to 18%, B203 content is 7 to 28%, BaO content is 0 to 5.5%, ZnO content is 1 to 18%, La203 content is 31 to 53%, Y203 content is 3% or less, Ti02 content is 7 to 45%, WO3 content is 0 to 0.5%, Zr02 content is 1 to 19%, CaO content is 1 to 13%, Na20 content is 0.8% or less, Gd203 content is 2% or less, Ta205 content is 2% or less. ​ The mass ratio of the total content of TiO2 and ZrO2 relative to the content of CaO ((TiO2+ZrO2) / CaO) is 3.35 or more; The mass ratio of the content of CaO relative to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.05 to 1.0; The mass ratio of the content of B2O3 relative to the content of SiO2 (B2O3 / SiO2) is 1.6 to 5.5; The total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) is 33 to 55%; The mass ratio of the content of B2O3 relative to the content of ZrO2 (B2O3 / ZrO2) is 0.4 to 5.7; The mass ratio of the content of Nb2O5 relative to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) is 0 to 0.2; The mass ratio of the content of TiO2 relative to the content of ZnO (TiO2 / ZnO) is 0.9 or more; The mass ratio of the content of Y2O3 relative to the content of B2O3 (Y2O3 / B2O3) is 0 to 0.3; The refractive index nd is 1.8800 to 1.9200; The Abbe number vd is 28 to 33; The specific gravity is 4.00 to 5.00; The glass transition temperature Tg is 600 to 670°C; λ 70 is 375-440 nm; λ5 is 350 to 370 nm.

11. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: The content of Nb2O5 is 0 to 3%; The content of SiO2 is 2 to 16%; The content of B2O3 is 9 to 26%; The content of BaO is 0.1 to 4.5%; The content of ZnO is 2 to 16%; The content of La2O3 is 33 to 51%; The content of Y2O3 is 2% or less; The content of TiO2 is 9 to 40%; The content of WO3 is 0 to 0.4%; The content of ZrO2 is 2 to 18%; The content of CaO is 2 to 12%; The content of Na2O is 0.4% or less; The content of Gd2O3 is 1% or less; The content of Ta2O5 is 1% or less; The mass ratio of the total content of TiO2 and ZrO2 relative to the content of CaO ((TiO2+ZrO2) / CaO) is 3.40 or more; The mass ratio of the content of CaO relative to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) is 0.10 to 0.8; The mass ratio of the content of B2O3 relative to the content of SiO2 (B2O3 / SiO2) is 1.7 to 5.0; The total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) is 36.4 to 55%; The mass ratio of the content of B2O3 relative to the content of ZrO2 (B2O3 / ZrO2) is 0.8 to 4.9; a mass ratio of the Nb2O5 content to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) of 0 to 0.15; a mass ratio of the TiO2 content to the ZnO content (TiO2 / ZnO) of 0.95 or more; a mass ratio of the Y2O3 content to the B2O3 content (Y2O3 / B2O3) of 0 to 0.2; a refractive index nd of 1.8850 to 1.9180; an Abbe number vd of 28.5 to 32.6; a specific gravity of 4.05 to 4.90; a glass transition temperature Tg of 604 to 668°C; λ 70 is 376-439 nm; λ5 of 352 to 368 nm.

12. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: the Nb2O5 content is 0 to 2% the SiO2 content is 3 to 12%; the B2O3 content is 11 to 24%; the BaO content is 0.1 to 3.5%; the ZnO content is 3 to 15%; the La2O3 content is 35 to 49%; the Y2O3 content is 1% or less; the TiO2 content is 11 to 30%; the WO3 content is 0 to 0.3%; the ZrO2 content is 3 to 17%; the CaO content is 2.5 to 11%; the Na2O content is 0%; the Gd2O3 content is 0%; the Ta2O5 content is 0%; a mass ratio of the total content of TiO2 and ZrO2 to the CaO content ((TiO2+ZrO2) / CaO) of 3.45 or more; a mass ratio of the CaO content to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) of 0.15 to 0.7; a mass ratio of the B2O3 content to the SiO2 content (B2O3 / SiO2) of 1.8 to 4.5; the total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) is 37 to 51%; a mass ratio of the B2O3 content to the ZrO2 content (B2O3 / ZrO2) of 1.2 to 4.1; a mass ratio of the Nb2O5 content to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) of 0 to 0.1; a mass ratio of the TiO2 content to the ZnO content (TiO2 / ZnO) of 1.00 or more; a mass ratio of the Y2O3 content to the B2O3 content (Y2O3 / B2O3) of 0 to 0.1; a refractive index nd of 1.8900 to 1.9160; an Abbe number vd of 29 to 32.2; a specific gravity of 4.10 to 4.85; a glass transition temperature Tg of 606 to 666°C; λ 70 is 378-438 nm; λ5 of 354 to 367 nm.

13. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: the Nb2O5 content is 0 to 1%; the SiO2 content is 4 to 10%; the B2O3 content is 12 to 22%; BaO content: 0.2 to 2.5%; La2O3 content: 37 to 47%; Y2O3 content: 0%; TiO2 content: 12 to 20%; WO3 content: 0 to 0.2%; ZrO2 content: 4 to 16%; CaO content: 3 to 10%; mass ratio of the total content of TiO2 and ZrO2 to the CaO content ((TiO2+ZrO2) / CaO) of 3.50 or more; mass ratio of the CaO content to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) of 0.20 to 0.60; mass ratio of the B2O3 content to the SiO2 content (B2O3 / SiO2) of 1.9 to 4.0; total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) of 38 to 49%; mass ratio of the B2O3 content to the ZrO2 content (B2O3 / ZrO2) of 1.6 to 3.3; mass ratio of the Nb2O5 content to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) of 0 to 0.05; mass ratio of the TiO2 content to the ZnO content (TiO2 / ZnO) of 1.10 or more; mass ratio of the Y2O3 content to the B2O3 content (Y2O3 / B2O3) of 0; refractive index nd of 1.8950 to 1.9120; Abbe number vd of 30 to 31.8; specific gravity of 4.15 to 4.80; glass transition temperature Tg of 610 to 664°C; λ 70 is 379-437 nm; λ5 of 355 to 366 nm.

14. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: Nb2O5 content: 0%; B2O3 content: 13 to 20%; BaO content: 0.2 to 1.5%; La2O3 content: 39 to 45%; WO3 content: 0 to 0.1%; ZrO2 content: 5 to 15%; mass ratio of the total content of TiO2 and ZrO2 to the CaO content ((TiO2+ZrO2) / CaO) of 3.55 or more; mass ratio of the CaO content to the total content of CaO, BaO, SrO, and ZnO (CaO / (CaO+BaO+SrO+ZnO)) of 0.20 to 0.50; mass ratio of the B2O3 content to the SiO2 content (B2O3 / SiO2) of 2.0 to 3.5; total content of La2O3, Gd2O3, and Y2O3 (La2O3+Gd2O3+Y2O3) of 39 to 45%; mass ratio of the Nb2O5 content to the total content of Nb2O5, TiO2, WO3, and Ta2O5 (Nb2O5 / (Nb2O5+TiO2+WO3+Ta2O5)) of 0; refractive index nd of 1.9000 to 1.9100; Abbe number vd of 31 to 31.6; specific gravity of 4.20 to 4.70; λ 70 is 380-436 nm; λ5 is 356 to 365 nm.

15. The optical glass according to any one of claims 1 to 9, which satisfies at least one of the following: the BaO content is 0.3 to 0.5%; the WO3 content is 0%.

16. An optical element comprising the optical glass according to any one of claims 1 to 15.

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