Optical glass and optical components

Abstract

The present invention provides an optical glass having desired optical constants and excellent stability during reheating, and an optical element made of the optical glass. The optical glass has an Abbe number νd of 36.40 or more, a SiO2 content of 25 to 55% by mass, a B2O3 content of 13% or less by mass, a Li2O content of 20% or less by mass, a Na2O content of 17% or less by mass, a ZrO2 content of 2 to 22% by mass, a Nb2O5 content of 12 to 42% by mass, a mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] of 2.00 or less, and a Li2O, Na2O and K The mass ratio of the total content R2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is greater than 0.60, the total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is greater than 93 mass%, and the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is less than 5.00.

Description

Technical Field

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

[0002] When glass is heated to a temperature higher than the glass transition temperature Tg, it softens. As a molding method for optical elements using this property, the following press molding method is known: the glass raw material obtained by heating and melting the glass raw material and molding is reheated to soften it, and then pressurized to mold it into a desired shape. At this time, by reheating the glass, there is a situation where the glass crystallizes and the glass loses transparency. For glass with excellent stability during reheating, it is not easy to crystallize due to reheating, and devitrification is also suppressed. In recent years, it is required to have higher stability during reheating.

[0003] Patent Document 1 discloses an optical glass having a given refractive index nd and Abbe number νd. However, it is known that the glass of Patent Document 1 does not necessarily satisfy the required stability.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-154963 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Therefore, an object of the present invention is to provide an optical glass having desired optical constants and excellent stability during reheating, and an optical element made of the optical glass.

[0009] Solutions to the problem

[0010] The gist of the present invention is as follows.

[0011] (1) An optical glass having an Abbe number νd of 36.40 or more,

[0012] The content of SiO2 is 25-55% by mass.

[0013] The content of B2O3 is 13% by mass or less,

[0014] The content of Li2O is 20 mass % or less,

[0015] The content of Na2O is 17% by mass or less,

[0016] The content of ZrO2 is 2 to 22% by mass.

[0017] The content of Nb2O5 is 12 to 42% by mass.

[0018] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0019] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more,

[0020] The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more,

[0021] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is less than 5.00.

[0022] (2) An optical glass having an Abbe number νd of 36.40 or more,

[0023] The content of SiO2 is 25-55% by mass.

[0024] The content of B2O3 is 13% by mass or less,

[0025] The content of Li2O is 20 mass % or less,

[0026] The content of Na2O is 17% by mass or less,

[0027] The content of ZrO2 is 2 to 22% by mass.

[0028] The content of Nb2O5 is 12 to 42% by mass.

[0029] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0030] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more,

[0031] The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more,

[0032] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less,

[0033] The mass ratio of the content of B2O3 to the content of SiO2 [B2O3 / SiO2] is 0.240 or less.

[0034] (3) An optical glass having an Abbe number νd of 36.40 or more,

[0035] The content of SiO2 is 25-55% by mass.

[0036] The content of B2O3 is 13% by mass or less,

[0037] The content of Li2O is 20 mass % or less,

[0038] The content of Na2O is 17% by mass or less,

[0039] The content of ZrO2 is 2 to 22% by mass.

[0040] The content of Nb2O5 is 12 to 42% by mass.

[0041] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0042] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more, the total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less,

[0043] The mass ratio of the content of B2O3 to the content of ZrO2 [B2O3 / ZrO2] is 1.05 or less.

[0044] (4) The optical glass according to any one of (1) to (3), wherein

[0045] The mass ratio of the content of Na2O to the total content of R2O of Li2O, Na2O and K2O [Na2O / R2O] is 0.80 or less.

[0046] (5) The optical glass according to any one of (1) to (4), wherein

[0047] The total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the total mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] are less than 1.30.

[0048] (6) The optical glass according to any one of (1) to (5), wherein

[0049] The mass ratio of the total content of R2O, Na2O and K2O to the content of ZrO2 [R2O / ZrO2] is 2.00 or less.

[0050] (7) An optical element made of the optical glass described in any one of (1) to (6) above.

[0051] Effects of the Invention

[0052] According to the present invention, it is possible to provide an optical glass having desired optical constants and excellent stability during reheating, and an optical element made of the optical glass. DETAILED DESCRIPTION

[0053] The following is an explanation of the embodiments of the present invention. It should be noted that, in the present invention and this specification, unless otherwise specified, the glass composition of the optical glass is expressed on an oxide basis. Here, "glass composition on an oxide basis" refers to the glass composition obtained by converting the glass raw materials into substances that are present in the form of oxides in the optical glass after they are completely decomposed during melting, and the expressions of the various glass components are usually recorded as SiO2, TiO2, etc. Unless otherwise specified, the content and total content of the glass components are on a mass basis, and "%" means "mass %".

[0054] The content of the glass component can be quantified by a known method, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), etc. In addition, in this specification and the present invention, the content of a constituent component of 0% means that the constituent component is substantially not contained, and the inclusion of the constituent component at an unavoidable impurity level is allowed.

[0055] In this specification, unless otherwise specified, the refractive index refers to the refractive index nd under helium d-ray (wavelength 587.56 nm).

[0056] Hereinafter, the optical glass of the present invention will be described in the form of a first embodiment, a second embodiment, and a third embodiment.

[0057] First Embodiment

[0058] The Abbe number νd of the optical glass of the first embodiment is 36.40 or more.

[0059] The content of SiO2 is 25-55%,

[0060] The content of B2O3 is less than 13%,

[0061] The content of Li2O is less than 20%,

[0062] The content of Na2O is less than 17%,

[0063] The content of ZrO2 is 2-22%,

[0064] The content of Nb2O5 is 12-42%,

[0065] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0066] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more,

[0067] The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is more than 93%, and the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is less than 5.00.

[0068] In the optical glass of the first embodiment, the Abbe number νd is 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50.

[0069] The Abbe number νd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components with relatively low Abbe number νd, i.e., highly dispersed components, include Nb2O5, TiO2, ZrO2, WO3, Bi2O3, Ta2O5, etc. On the other hand, components with relatively high Abbe number νd, i.e., low dispersed components, include SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, SrO, etc.

[0070] In the optical glass of the first embodiment, the content of SiO2 is 25-55%. The lower limit of the content of SiO2 is preferably 27%, and more preferably 29%, 30%, 31%, 32%, and 33% in the following order. In addition, the upper limit of the content of SiO2 is preferably 53%, and more preferably 50%, 48%, 46%, 44%, 42%, 40%, and 38% in the following order. SiO2 is a network-forming component of glass. When the content of SiO2 is too little, there is a concern that the stability during reheating is reduced. In addition, when the content of SiO2 is too much, there is a concern that the high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases.

[0071] In the optical glass of the first embodiment, the content of B2O3 is 13% or less. The upper limit of the content of B2O3 is preferably 12%, and more preferably 11%, 10%, 9%, and 8% in the following order. In addition, the lower limit of the content of B2O3 is preferably 0%, and more preferably 1%, 2%, and 3% in the following order. The content of B2O3 may also be 0%. B2O3 is a network-forming component of glass. When the content of B2O3 is too much, there is a concern that high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases. When the content of B2O3 is too little, there is a concern that stability during reheating is reduced.

[0072] In the glass of the first embodiment, the content of Li2O is 20% or less. The upper limit of the content of Li2O is preferably 18%, and more preferably 17%, 16%, 15%, 14%, 13%, and 12% in the following order. In addition, the lower limit of the content of Li2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 8% in the following order. Li2O is a component that contributes to low viscosity and low Pg, F of glass. When the content of Li2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Li2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0073] In the glass of the first embodiment, the content of Na2O is 17% or less. The upper limit of the content of Na2O is preferably 16%, and more preferably 15%, 14%, 13%, 12%, 11%, 10%, and 9% in the following order. The lower limit of the content of Na2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, and 5% in the following order. The content of Na2O may also be 0%. Na2O, like Li2O, is a component that contributes to low viscosity and low Pg, F of glass. When the content of Na2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Na2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0074] In the glass of the first embodiment, the content of ZrO2 is 2 to 22%. The lower limit of the content of ZrO2 is preferably 4%, and more preferably 5%, 6%, 7%, 8%, and 9% in the following order. In addition, the upper limit of the content of ZrO2 is preferably 20%, and more preferably 18%, 16%, 15%, 14%, and 13% in the following order. ZrO2 is a component that contributes to low Pg, F. When the content of ZrO2 is too much, there is a concern that the liquidus temperature LT will rise. In addition, when the content of ZrO2 is too little, there is a concern that Pg, F will rise.

[0075] In the optical glass of the first embodiment, the content of Nb2O5 is 12 to 42%. The lower limit of the content of Nb2O5 is preferably 14%, and more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24%, and 25% in the following order. In addition, the upper limit of the content of Nb2O5 is preferably 40%, and more preferably 38%, 36%, 34%, 33%, 32%, 31%, and 30% in the following order. Nb2O5 is a component that helps to achieve both high dispersion and low Pg, F. When the content of Nb2O5 is too much, there is a concern that the stability during reheating is reduced, and there is a concern that the solubility is reduced. When the content of Nb2O5 is too little, there is a concern that low dispersion is achieved.

[0076] In the optical glass of the first embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, and more preferably 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1.70 in the following order. In addition, the lower limit of the mass ratio is preferably 1.00, and more preferably 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40 in the following order. By setting the mass ratio to the above range, the Abbe number νd can be controlled to a desired range. If the mass ratio is too large, the Abbe number νd may exceed the desired range. If the mass ratio is too small, the stability during reheating may be reduced.

[0077] In the optical glass of the first embodiment, the mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, and further preferably 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 in the following order. In addition, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio to the above range, the Pg,F of the glass can be reduced. If the mass ratio is too small, there is a concern that ΔPg,F represented by formula [8] described later will increase.

[0078] In the optical glass of the first embodiment, the total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, and more preferably 95%, 96%, 97%, 98%, 99% in the following order. In addition, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, there is a concern that the coloring of the glass increases, and there is a concern that the desired optical constants cannot be obtained, the stability during reheating, etc. deteriorates, and there is also a concern that the cost of raw materials for the glass increases.

[0079] In the optical glass of the first embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.00 or less. The upper limit of the mass ratio is preferably 4.80, and more preferably 4.70, 4.50, 4.40, 4.30, 4.20, 4.10, 4.00 in the following order. In addition, the lower limit of the mass ratio is preferably 2.00, and more preferably 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40, 3.50 in the following order. By setting the mass ratio to the above range, it is possible to take into account both low Pg, F and improved stability during reheating. When the mass ratio is too large, there is a concern that Pg, F will rise. If the mass ratio is too small, the liquidus temperature LT may increase, and the stability during reheating may decrease.

[0080] In the optical glass of the first embodiment, the upper limit of the mass ratio of the content of B2O3 to the content of SiO2 [B2O3 / SiO2] is preferably 0.240, and more preferably 0.238, 0.236, 0.234, 0.232, 0.230 in the following order. The lower limit of the mass ratio is preferably 0.020, and more preferably 0.030, 0.040, 0.050, 0.060 in the following order. By setting the mass ratio to the above range, the specific gravity can be reduced and the transmittance can be increased.

[0081] In the optical glass of the first embodiment, the upper limit of the mass ratio [B2O3 / ZrO2] of the content of B2O3 to the content of ZrO2 is preferably 1.05, and more preferably 1.00, 0.95, 0.90, 0.85, 0.80, and 0.75 in the following order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, and 0.20 in the following order. By setting the mass ratio to the above range, Pg, F can be reduced.

[0082] In the optical glass of the first embodiment, the upper limit of the mass ratio [Na2O / R2O] of the content of Na2O to the total content R2O of Li2O, Na2O and K2O is preferably 0.80, and more preferably 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66, 0.65 in the following order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed.

[0083] In the optical glass of the first embodiment, the upper limit of the total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] is preferably 1.30, and more preferably 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00 in the following order. The lower limit of the total is preferably 0.30, and more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in the following order. By setting the total in the above range, a decrease in stability during reheating can be suppressed.

[0084] In the optical glass of the first embodiment, the upper limit of the mass ratio [R2O / ZrO2] of the total content of Li2O, Na2O and K2O to the content of ZrO2 is preferably 2.00, and more preferably 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1.66, 1.64, 1.62, 1.60 in the following order. The lower limit of the mass ratio is preferably 1.00, and more preferably 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed, and the increase in Pg, F can be suppressed.

[0085] (Glass composition)

[0086] Non-limiting examples are shown below about the contents and ratios of the glass components other than those described above in the optical glass of the first embodiment.

[0087] In the optical glass of the first embodiment, the upper limit of the content of P2O5 is preferably 10.0%, and further preferably 9.0%, 8.0%, 7.0%, 6.0%, 5.0%, and 4.0% in the following order. In addition, the lower limit of the content of P2O5 is preferably 0%, and further may be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3.0%. The content of P2O5 may also be 0%. By setting the content of P2O5 to the above range, the increase of the relative partial dispersion Pg, F can be suppressed and the thermal stability of the glass can be maintained.

[0088] In the optical glass of the first embodiment, the upper limit of the total content [SiO2+B2O3+P2O5] of SiO2, B2O3 and P2O5 is preferably 50.0%, and more preferably 49.5%, 49.0%, 48.5%, 48.0%, 47.5%, 47.0%, 46.5%, 46.0%, 45.5%, 45.0% in the following order. In addition, the lower limit of the total content [SiO2+B2O3+P2O5] is preferably 30.0%, and more preferably 31.0%, 32.0%, 33.0%, 34.0%, 35.0%, 36.0%, 37.0%, 38.0%, 39.0%, 40.0% in the following order.

[0089] In the optical glass of the first embodiment, the upper limit of the content of Al2O3 is preferably 20.0%, and more preferably 15.0%, 10.0%, 5.0%, 3.0%, and 1.0% in the following order. The content of Al2O3 may also be 0%. By setting the content of Al2O3 to the above range, the devitrification resistance and thermal stability of the glass can be maintained.

[0090] In the optical glass of the first embodiment, the upper limit of the content of K2O is preferably 25.0%, and more preferably 20.0%, 18.0%, 16.0%, 14.0%, 12.0%, 10.0%, 5.0%, 2.0%, and 1.0% in the following order. The lower limit of the content of K2O is preferably 0%, and more preferably 0.5%. The content of K2O may be 0%.

[0091] K2O is a component that contributes to the reduction of relative partial dispersion Pg, F, and has the effect of lowering the liquidus temperature and improving the thermal stability of the glass, but when its content increases, chemical durability, weather resistance, and stability during reheating decrease. Therefore, the content of K2O is preferably within the above range.

[0092] In the optical glass of the first embodiment, the upper limit of the total content R2O [Li2O+Na2O+K2O] of Li2O, Na2O and K2O is preferably 25.0%, and more preferably 24.0%, 23.0%, 22.0%, 21.0%, and 20.0% in the following order. In addition, the lower limit of the total content R2O is preferably 5.0%, and more preferably 6.0%, 7.0%, 8.0%, 9.0%, and 10.0% in the following order. By setting the total content R2O to the above range, the viscosity of the glass can be reduced, and the increase of Pg, F can be suppressed.

[0093] In the optical glass of the first embodiment, the upper limit of the content of Cs2O is preferably 10%, and more preferably 5%, 3%, and 1% in the following order. The lower limit of the content of Cs2O is preferably 0%.

[0094] Cs2O has the effect of improving the thermal stability of glass, but when its content increases, chemical durability and weather resistance decrease. Therefore, the content of Cs2O is preferably within the above range.

[0095] In the optical glass of the first embodiment, the upper limit of the content of TiO2 is preferably 15.0%, and further preferably 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0%, 5.0% in the following order. In addition, the lower limit of the content of TiO2 is preferably 0%, and further can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3.0%. The content of TiO2 can also be 0%. By setting the content of TiO2 to the above range, the desired optical constants can be achieved, and the increase of Pg, F can be suppressed, and the increase of specific gravity can be suppressed.

[0096] In the optical glass of the first embodiment, the upper limit of the content of WO3 is preferably 5%, and more preferably 4%, 3%, and 2% in the following order. The content of WO3 may also be 0%. By setting the content of WO3 to the above range, the transmittance can be increased, and the relative partial dispersion Pg, F and specific gravity can be reduced.

[0097] In the optical glass of the first embodiment, the upper limit of the content of Bi2O3 is preferably 5%, and more preferably 4%, 3%, and 2% in the following order. In addition, the lower limit of the content of Bi2O3 is preferably 0%. By setting the content of Bi2O3 to the above range, the transmittance can be increased, and the relative partial dispersion Pg, F and specific gravity can be reduced.

[0098] In the optical glass of the first embodiment, the upper limit of the mass ratio of the total content of Nb2O5, TiO2 and ZrO2 to the total content of SiO2 and B2O3 [(Nb2O5+TiO2+ZrO2) / (SiO2+B2O3)] is preferably 1.50, and more preferably 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.15, 1.10, 1.05, 1.00 in the following order. The lower limit of the mass ratio is preferably 0.50, and more preferably 0.55, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76 in the following order. By setting the mass ratio to the above range, the refractive index can be within a desired range.

[0099] In the optical glass of the first embodiment, the upper limit of the content of Ta2O5 is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0% in the following order. In addition, the lower limit of the content of Ta2O5 is preferably 0%.

[0100] Ta2O5 is a glass component that improves the thermal stability of glass and is a component that reduces the relative partial dispersion Pg, F. On the other hand, when the content of Ta2O5 increases, the raw material cost increases and the specific gravity increases. Therefore, the content of Ta2O5 is preferably within the above range.

[0101] In the optical glass of the first embodiment, the upper limit of the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [Nb2O5+TiO2+Bi2O3+WO3+Ta2O5] is preferably 40.0%, and more preferably 39.0%, 38.0%, 37.0%, 36.0%, 35.0%, 34.0%, 33.0%, 32.0%, 31.0%, 30.0% in the following order. The lower limit of the total content is preferably 15.0%, and more preferably 16.0%, 17.0%, 18.0%, 19.0%, 20.0%, 21.0%, 22.0%, 23.0% in the following order.

[0102] In the optical glass of the first embodiment, the upper limit of the mass ratio of the content of Ta2O5 to the content of ZrO2 [Ta2O5 / ZrO2] is preferably 0.45, and more preferably 0.40, 0.35, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05 in the following order. The lower limit of the mass ratio is preferably 0, and the mass ratio is more preferably 0. By setting the mass ratio to the above range, the optical constants can be within the desired range, and the raw material cost of the glass can be reduced.

[0103] In the optical glass of the first embodiment, the upper limit of the mass ratio of the total content of SiO2, B2O3, P2O5, Nb2O5, TiO2 and WO3 to the total content of Li2O, Na2O, K2O and ZrO2 [(SiO2+B2O3+P2O5+Nb2O5+TiO2+WO3) / (Li2O+Na2O+K2O+ZrO2)] is preferably 3.50, and more preferably 3.40, 3.30, 3.20, 3.10, 3.00 in the following order. The lower limit of the mass ratio is preferably 1.70, and more preferably 1.80, 1.90, 2.00, 2.10 in the following order.

[0104] In the optical glass of the first embodiment, the upper limit of the mass ratio [(SiO2+B2O3+P2O5) / R2O] of the total content of SiO2, B2O3 and P2O5 to the total content R2O of Li2O, Na2O and K2O is preferably 4.00, and more preferably 3.80, 3.60, and 3.40 in the following order. The lower limit of the mass ratio is preferably 1.50, and more preferably 1.60, 1.70, 1.80, 1.90, and 2.00 in the following order.

[0105] In the optical glass of the first embodiment, the upper limit of the mass ratio of the content of Nb2O5 to the content of ZrO2 [Nb2O5 / ZrO2] is preferably 3.20, and more preferably 2.90, 2.70, and 2.50 in the following order. The lower limit of the mass ratio is preferably 1.20, and more preferably 1.40, 1.60, and 1.80 in the following order.

[0106] In the optical glass of the first embodiment, the upper limit of the total mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Li2O, Na2O and K2O R2O, and the mass ratio of the content of Nb2O5 to the content of ZrO2 [{(SiO2+B2O3+P2O5) / R2O}+(Nb2O5 / ZrO2)] is preferably 6.20, and more preferably 5.80, 5.60, 5.50, 5.10, 5.00 in the following order. The lower limit of the mass ratio is preferably 3.00, and more preferably 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 3.95, 4.00, 4.05, 4.10 in the following order.

[0107] In the optical glass of the first embodiment, the upper limit of the MgO content is preferably 20%, and more preferably 10%, 5%, and 3% in the following order. In addition, the lower limit of the MgO content is preferably 0%.

[0108] In the optical glass of the first embodiment, the upper limit of the CaO content is preferably 20%, and more preferably 18%, 16%, and 14% in the following order. In addition, the lower limit of the CaO content is preferably 0%, and more preferably 1.0%, 1.5%, and 2.0% in the following order.

[0109] In the optical glass of the first embodiment, the upper limit of the SrO content is preferably 20%, and more preferably 10%, 5%, and 3% in the following order. In addition, the lower limit of the SrO content is preferably 0%.

[0110] In the optical glass of the first embodiment, the upper limit of the BaO content is preferably 10%, and more preferably 5.0%, 3.0%, and 2.0% in the following order. The lower limit of the BaO content is preferably 0%.

[0111] MgO, CaO, SrO, and BaO are all glass components that have the effect of improving the thermal stability and devitrification resistance of glass. However, when the content of these glass components increases, the specific gravity increases, the high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, the contents of each of these glass components are preferably within the above ranges.

[0112] In the optical glass of the first embodiment, the upper limit of the content of ZnO is preferably 10%, and more preferably 5.0%, 3.0%, and 2.0% in the following order. In addition, the lower limit of the content of ZnO is preferably 0%.

[0113] ZnO is a glass component that has the effect of improving the thermal stability of glass. However, when the content of ZnO is too much, the specific gravity rises. Therefore, from the viewpoint of improving the thermal stability of glass and maintaining the desired optical constants, the content of ZnO is preferably within the above range.

[0114] In the optical glass of the first embodiment, the upper limit of the total content R0 of MgO, CaO, SrO, BaO and ZnO [MgO+CaO+SrO+BaO+ZnO] is preferably 20.0%, and more preferably 15.0%, 10.0%, 8.0%, 6.0%, 4.0% and 3.0% in the following order. The lower limit of the total content is preferably 0%. By setting the total content to the above range, the refractive index nd can be within a desired range.

[0115] In the optical glass of the first embodiment, the upper limit of the mass ratio [RO / ZrO2] of the total content RO of MgO, CaO, SrO, BaO and ZnO to the content of ZrO2 is preferably 0.74, and more preferably 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, 0.10 in the following order. The lower limit of the mass ratio is preferably 0. By setting the mass ratio to the above range, Pg, F can be reduced, and the refractive index nd can be within a desired range.

[0116] In the glass of the first embodiment, the upper limit of the content of Y2O3 is preferably 20%, and more preferably 10%, 5%, and 3% in the following order. In addition, the lower limit of the content of Y2O3 is preferably 0%.

[0117] When the content of Y2O3 is too much, the thermal stability of the glass decreases, and the glass is easily devitrified during manufacture. In addition, there is a concern that the high dispersibility is impaired. Therefore, from the viewpoint of suppressing the reduction of the thermal stability of the glass, the content of Y2O3 is preferably within the above range.

[0118] In the glass of the first embodiment, the content of Sc2O3 is preferably 2% or less. In addition, the lower limit of the content of Sc2O3 is preferably 0%.

[0119] In the glass of the first embodiment, the content of HfO2 is preferably 2% or less. In addition, the lower limit of the content of HfO2 is preferably 0%.

[0120] Sc2O3 and HfO2 have the effect of improving the high dispersibility of glass, but they are expensive components. Therefore, the content of each of Sc2O3 and HfO2 is preferably within the above range.

[0121] In the glass of the first embodiment, the content of Lu2O3 is preferably 2% or less. In addition, the lower limit of the content of Lu2O3 is preferably 0%.

[0122] Lu2O3 has the effect of improving the high dispersibility of glass, but due to its large molecular weight, it is also a glass component that increases the specific gravity of glass. Therefore, the content of Lu2O3 is preferably within the above range.

[0123] In the glass of the first embodiment, the content of GeO2 is preferably 2% or less. In addition, the lower limit of the content of GeO2 is preferably 0%.

[0124] GeO2 has the effect of improving the high dispersibility of glass, but is a significantly expensive component in the glass components generally used. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO2 is preferably within the above range.

[0125] In the optical glass of the first embodiment, the upper limit of the content of La2O3 is preferably 10.0%, and more preferably 9.0%, 8.0%, 7.0%, 6.0%, 5.0%, and 4.0% in the following order. In addition, the lower limit of the content of La2O3 is preferably 0.1%, and more preferably 0.2%, 0.3%, and 0.4% in the following order. The content of La2O3 may also be 0%. By setting the upper limit of the content of La2O3 to the above range, the increase in specific gravity can be suppressed.

[0126] In the glass of the first embodiment, the content of Gd2O3 is preferably 2% or less. In addition, the lower limit of the content of Gd2O3 is preferably 0%.

[0127] When the content of Gd2O3 is too much, the thermal stability of the glass decreases. In addition, when the content of Gd2O3 is too much, the specific gravity of the glass increases, which is not preferred. Moreover, there is a concern about the increase in raw material costs. Therefore, from the viewpoint of maintaining the thermal stability of the glass well and suppressing the increase in specific gravity, the content of Gd2O3 is preferably within the above range.

[0128] In the glass of the first embodiment, the content of Yb2O3 is preferably 2% or less. In addition, the lower limit of the content of Yb2O3 is preferably 0%.

[0129] Compared with La2O3, Gd2O3, and Y2O3, Yb2O3 has a large molecular weight, so it increases the specific gravity of the glass. In addition, when the content of Yb2O3 is too much, the thermal stability of the glass decreases. From the perspective of preventing the decrease in the thermal stability of the glass and suppressing the increase in specific gravity, the content of Yb2O3 is preferably within the above range.

[0130] The glass of the first embodiment is preferably mainly composed of the above-mentioned glass components, that is, SiO2, ZrO2, and Nb2O5 as essential components, and B2O3, Li2O, Na2O, P2O5, Al2O3, K2O, Cs2O, TiO2, WO3, Bi2O3, Ta2O5, MgO, CaO, SrO, BaO, ZnO, Y2O3, Sc2O3, HfO2, Lu2O3, GeO2, La2O3, Gd2O3, and Yb2O3 as optional components. The total content of the above-mentioned glass components is preferably 95% or more, more preferably 98% or more, further preferably 99% or more, and particularly preferably 99.5% or more.

[0131] It should be noted that the glass of the first embodiment is preferably basically composed of the above-mentioned glass components, but may contain other components within a range that does not hinder the effects of the present invention. In addition, the present invention does not exclude the inclusion of inevitable impurities.

[0132] In addition to the above components, the optical glass may contain a small amount of Sb2O3 as a clarifier, etc. The total amount of the clarifier (external addition amount) is preferably 0% or more and less than 1%, more preferably 0% or more and 0.5% or less.

[0133] The added amount in the external addition ratio refers to a value expressed as a weight percentage of the added amount of the clarifier when the total content of all glass components excluding the clarifier is set to 100%.

[0134] Pb, As, Ce, Th, etc. are components that may cause environmental burden. Therefore, the content of each of Pb, As, Ce, and Th is preferably 0 to 0.1% in terms of oxide, more preferably 0 to 0.05%, and even more preferably 0 to 0.01%. It is particularly preferred that Pb, As, Ce, and Th are substantially not contained.

[0135] In addition, the optical glass can obtain high transmittance in a wide range of the visible region. In order to effectively utilize such a feature, it is preferably free of coloring elements. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, and V. Any element is preferably less than 100 mass ppm, more preferably 0 to 80 mass ppm, further preferably 0 to 50 mass ppm, and particularly preferably substantially free of.

[0136] In addition, Ga, Te, Tb, etc. are components that do not need to be introduced and are also expensive components. Therefore, the range of the content of Ga2O3, TeO2, and TbO2 expressed by mass% is preferably 0 to 0.1%, more preferably 0 to 0.05%, further preferably 0 to 0.01%, further preferably 0 to 0.005%, further preferably 0 to 0.001%, and particularly preferably substantially free of Ga2O3, TeO2, and TbO2.

[0137] (Glass properties)

[0138] <Refractive index nd>

[0139] In the optical glass of the first embodiment, the refractive index nd is preferably 1.80 to 1.50. The refractive index nd may be 1.75 to 1.55 or 1.70 to 1.60.

[0140] The refractive index nd can be made to be a desired value by appropriately adjusting the content of each glass component. The components (high refractive index components) having the effect of relatively increasing the refractive index nd are Nb2O5, TiO2, ZrO2, Ta2O5, La2O3, etc. On the other hand, the components (low refractive index components) having the effect of relatively reducing the refractive index nd are SiO2, B2O3, Li2O, Na2O, K2O, etc. In addition, for example, the refractive index nd can be increased by increasing the mass ratio [(Nb2O5+TiO2+ZrO2) / (SiO2+B2O3)] of the total content of the high refractive index components Nb2O5, TiO2 and ZrO2 and the total content of the low refractive index components SiO2 and B2O3, and the refractive index nd can be reduced by reducing this mass ratio.

[0141] <Relative partial dispersion Pg,F>

[0142] In the optical glass of the first embodiment, the upper limit of the relative partial dispersion Pg, F is preferably 0.5850, and further preferably 0.5845, 0.5840, 0.5835, 0.5830, 0.5825, 0.5820, 0.5815, 0.5810, 0.5805, 0.5800, 0.5795, 0.5790, 0.5785, 0.5780, 0.5775, 0.5770, 0.5765, 0.5760 in the following order. By setting the relative partial dispersion Pg, F to the above range, an optical glass suitable for high-order chromatic aberration correction can be obtained. On the other hand, the lower limit of the relative partial dispersion Pg, F is not particularly limited, and 0.5700 is set as a target.

[0143] In the optical glass of the first embodiment, the relative partial dispersion Pg,F preferably satisfies the following formula [1].

[0144] Pg,F≤0.6483-0.001802×νd···〔1〕

[0145] The relative partial dispersion Pg,F more preferably satisfies the following formula [2], and further more preferably satisfies the following formula [3], the following formula [4], the following formula [5], the following formula [6], and the following formula [7] in the following order.

[0146] Pg,F≤0.6470-0.001802×νd···〔2〕

[0147] Pg,F≤0.6460-0.001802×νd···〔3〕

[0148] Pg,F≤0.6450-0.001802×νd···〔4〕

[0149] Pg, F≤0.6444-0.001802×vd···〔5〕

[0150] Pg, F≤0.6439-0.001802×νd···〔6〕

[0151] Pg, F≤0.6437-0.001802×νd···〔7〕

[0152] By making the relative partial dispersion Pg,F satisfy the above formula, it is possible to satisfactorily correct chromatic aberration in a wide wavelength range for an optical element made of the optical glass of the first embodiment.

[0153] In the present invention, the Abbe number νd and the relative partial dispersion Pg, F are calculated as follows. That is, the refractive index at 12 wavelengths shown in Table A is measured by Japanese Industrial Standard (JIS standard) JIS B 7071-1 Method for measuring the refractive index of optical glass - Part 1: Minimum deviation angle method. Next, the refractive index of each ray obtained by the measurement is substituted into the Schott dispersion formula specified in Appendix B of Japanese Industrial Standard (JIS standard) JIS B 7071-1 Method for measuring the refractive index of optical glass - Part 1: Minimum deviation angle method, and the constant of the Schott dispersion formula is obtained by the least square method. Then, the Abbe number νd and the relative partial dispersion Pg, F are calculated based on the refractive index value of each ray obtained using the Schott dispersion formula with the constant determined.

[0154] Table A

[0155] Wavelength (nm) Spectral rays light source 1013.98 T-ray (infrared mercury) Hg 852.11 S-ray (infrared cesium) Cs 706.52 R-rays (red helium) He 656.27 C rays (red hydrogen) H 643.85 C′ rays (red cadmium) Cd 587.56 d-rays (yellow helium) He 546.07 e-ray (green mercury) Hg 486.13 F rays (blue hydrogen) H 479.99 F' rays (blue cadmium) Cd 435.84 g-rays (blue mercury) Hg 404.66 H-rays (purple mercury) Hg 365.01 I-ray (ultraviolet mercury) Hg

[0156] Schott distributed: n 2 =a0+a1λ 2 +a2λ -2 +a3λ -4 +a4λ -6 +a5λ -8

[0157] Where n is the refractive index, λ is the wavelength (μm), and a0, a1, a2, a3, a4, and a5 are constants.

[0158] In the present invention, the relative partial dispersion Pg,F is calculated as described above: using the values ​​of the refractive index measured at 12 different wavelengths (spectral rays), the coefficients of the wavelength term of the formula that relates the refractive index to the wavelength, called the Schott dispersion formula, are fitted and obtained, and after these coefficients are determined, the dispersion formula is used for calculation. By using the values ​​of the refractive index measured at 12 different wavelengths, the relative partial dispersion Pg,F can be calculated with high accuracy. On the other hand, the relative partial dispersion Pg,F can also be calculated by a simplified method by reducing the number of wavelengths for measuring the refractive index, but the accuracy is not sufficient, and the relative partial dispersion Pg,F calculated by the simplified method tends to be a smaller value than the value calculated by using the refractive index measured at 12 different wavelengths. That is, even if the value of the relative partial dispersion Pg,F is the same, there may be a situation where the actual performance related to chromatic aberration correction is superior or inferior due to the calculation method. Specifically, the relative partial dispersion Pg,F calculated by the simplified method as described above is estimated to be small, so even if the value of Pg,F is the same as the relative partial dispersion Pg,F calculated from the refractive index measured at 12 different wavelengths, there is a case where the actual performance related to chromatic aberration correction is poor.

[0159] In addition, ΔPg,F is a deviation from the normal line Pg,F and is obtained as shown in Formula [8].

[0160] ΔPg,F=Pg,F-(0.6483-0.001802×νd)···〔8〕

[0161] Generally speaking, in optical glass, there is a tendency that the smaller the Abbe number νd is, the larger Pg,F is. Therefore, ΔPg,F is usually used as an index of abnormal dispersion.

[0162] <Specific gravity of glass>

[0163] The specific gravity of the optical glass of the first embodiment is preferably 3.30 or less, more preferably 3.20 or less, and further preferably 3.10 or less.

[0164] The components that relatively increase the specific gravity are BaO, La2O3, ZrO2, Nb2O5, Ta2O5, etc. On the other hand, the components that relatively decrease the specific gravity are SiO2, B2O3, Li2O, Na2O, K2O, etc. The specific gravity can be controlled by appropriately adjusting the contents of these components.

[0165] <Stability during reheating>

[0166] In the optical glass of the first embodiment, when heated at the glass transition temperature Tg for 10 minutes and further heated at a temperature 220°C higher than the Tg for 10 minutes, the number of crystals observed per 1g is preferably 25 or less, more preferably 20 or less, and further preferably 10 or less.

[0167] It should be noted that the stability during reheating is evaluated as follows. A glass sample of 1 cm × 1 cm × 1 cm size is heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass sample, and further heated for 10 minutes in a second test furnace set to a temperature 220°C higher than its glass transition temperature Tg, and then an optical microscope (observation magnification: 40 to 100 times) is used to confirm the presence or absence of crystallization. Then, the average number of crystals per 1 g is measured. When the number of crystals is small, it can be evaluated as high stability, and when the number of crystals is large, it can be evaluated as low stability.

[0168] <Glass transition temperature Tg>

[0169] The upper limit of the glass transition temperature Tg of the optical glass of the first embodiment is preferably 650° C., and more preferably 640° C., 630° C., 620° C., 610° C., 600° C., 590° C., 580° C., 570° C., and 560° C. in the following order. In addition, the lower limit of the glass transition temperature Tg is preferably 430° C., and more preferably 440° C., 450° C., 460° C., and 470° C. in the following order. The glass transition temperature Tg can be controlled by adjusting the content of each glass component.

[0170] The components that relatively lower the glass transition temperature Tg are Li2O, Na2O, K2O, etc. The components that relatively raise the glass transition temperature Tg are La2O3, ZrO2, Nb2O5, etc. The glass transition temperature Tg can be controlled by appropriately adjusting the contents of these components.

[0171] <Light Transmission of Glass>

[0172] The light transmittance of the optical glass according to the first embodiment can be evaluated by the coloring degrees λ80 and λ5.

[0173] The spectral transmittance of a glass sample having a thickness of 10.0 mm±0.1 mm in the wavelength range of 200 to 700 nm was measured, and the wavelength at which the external transmittance became 80% was defined as λ80, and the wavelength at which the external transmittance became 5% was defined as λ5.

[0174] The λ80 of the optical glass of the first embodiment is preferably 500 nm or less, more preferably 470 nm or less, and further preferably 450 nm or less. The λ5 is preferably 370 nm or less, more preferably 360 nm or less, and further preferably 350 nm or less.

[0175] (Manufacture of optical glass)

[0176] The glass of the first embodiment is prepared by mixing glass raw materials in a manner to achieve the above-mentioned given composition, and the prepared glass raw materials are used to make it according to a known glass manufacturing method. For example, a plurality of compounds are mixed and fully mixed to form a batch of raw materials, and the batch of raw materials is placed in a quartz crucible or a platinum crucible for rough melting. The molten material obtained by the rough melting is quenched and crushed to make cullet. The cullet is further placed in a platinum crucible for heating and remelting to make molten glass. After further clarification and homogenization, the molten glass is formed and slowly cooled to obtain optical glass. The forming and slow cooling of the molten glass can be carried out by known methods.

[0177] It should be noted that as long as the desired glass components can be introduced into the glass and the desired content is achieved, there is no particular limitation on the compounds used in preparing the batch raw materials. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, fluorides, and the like.

[0178] (Manufacture of optical components, etc.)

[0179] When the optical glass of the first embodiment is used to make an optical element, a known method can be used. For example, in the manufacture of the above-mentioned optical glass, molten glass is injected into a mold and formed into a plate-like shape to make a glass material formed by the optical glass of the present invention. The obtained glass material is appropriately cut, ground, and polished to make fragments of a size and shape suitable for press molding. The fragments are heated and softened, and press molding (re-hot pressing) is performed by a known method to make an optical element blank with a shape similar to that of the optical element. The optical element blank is annealed, and the optical element is made by grinding and polishing by a known method.

[0180] Depending on the intended use, the optical functional surface of the manufactured optical element may be coated with an anti-reflection film, a total reflection film, or the like.

[0181] According to one embodiment of the present invention, an optical element formed by the above optical glass can be provided. As the type of optical element, lenses such as spherical lenses and aspherical lenses, prisms, diffraction gratings, etc. can be exemplified. As the shape of the lens, various shapes such as biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses can be exemplified. The optical element can be manufactured by a method including a step of processing a glass molded body formed by the above optical glass. As processing, cutting, machining, rough grinding, fine grinding, grinding, etc. can be exemplified. When performing such processing, by using the above glass, breakage can be reduced, and high-quality optical elements can be stably provided.

[0182] Second Embodiment

[0183] The Abbe number νd of the optical glass of the second embodiment is 36.40 or more.

[0184] The content of SiO2 is 25-55%,

[0185] The content of B2O3 is less than 13%,

[0186] The content of Li2O is less than 20%,

[0187] The content of Na2O is less than 17%,

[0188] The content of ZrO2 is 2-22%,

[0189] The content of Nb2O5 is 12-42%,

[0190] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0191] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more,

[0192] The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more,

[0193] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less,

[0194] The mass ratio of the content of B2O3 to the content of SiO2 [B2O3 / SiO2] is 0.240 or less.

[0195] In the optical glass of the second embodiment, the Abbe number νd is 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50.

[0196] The Abbe number νd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components with relatively low Abbe number νd, i.e., highly dispersed components, include Nb2O5, TiO2, ZrO2, WO3, Bi2O3, Ta2O5, etc. On the other hand, components with relatively high Abbe number νd, i.e., low dispersed components, include SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, SrO, etc.

[0197] In the optical glass of the second embodiment, the content of SiO2 is 25-55%. The lower limit of the content of SiO2 is preferably 27%, and more preferably 29%, 30%, 31%, 32%, and 33% in the following order. In addition, the upper limit of the content of SiO2 is preferably 53%, and more preferably 50%, 48%, 46%, 44%, 42%, 40%, and 38% in the following order. SiO2 is a network-forming component of glass. When the content of SiO2 is too little, there is a concern that the stability during reheating is reduced. In addition, when the content of SiO2 is too much, there is a concern that the high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases.

[0198] In the optical glass of the second embodiment, the content of B2O3 is 13% or less. The upper limit of the content of B2O3 is preferably 12%, and more preferably 11%, 10%, 9%, and 8% in the following order. In addition, the lower limit of the content of B2O3 is preferably 0%, and more preferably 1%, 2%, and 3% in the following order. The content of B2O3 may also be 0%. B2O3 is a network-forming component of glass. When the content of B2O3 is too much, there is a concern that high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases. When the content of B2O3 is too little, there is a concern that stability during reheating is reduced.

[0199] In the glass of the second embodiment, the content of Li2O is 20% or less. The upper limit of the content of Li2O is preferably 18%, and more preferably 17%, 16%, 15%, 14%, 13%, and 12% in the following order. In addition, the lower limit of the content of Li2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 8% in the following order. Li2O is a component that contributes to low viscosity and low Pg, F of glass. When the content of Li2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Li2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0200] In the glass of the second embodiment, the content of Na2O is 17% or less. The upper limit of the content of Na2O is preferably 16%, and more preferably 15%, 14%, 13%, 12%, 11%, 10%, and 9% in the following order. The lower limit of the content of Na2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, and 5% in the following order. The content of Na2O may also be 0%. Na2O, like Li2O, is a component that contributes to low viscosity and low Pg, F of glass. When the content of Na2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Na2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0201] In the glass of the second embodiment, the content of ZrO2 is 2 to 22%. The lower limit of the content of ZrO2 is preferably 4%, and more preferably 5%, 6%, 7%, 8%, and 9% in the following order. In addition, the upper limit of the content of ZrO2 is preferably 20%, and more preferably 18%, 16%, 15%, 14%, and 13% in the following order. ZrO2 is a component that contributes to low Pg, F. When the content of ZrO2 is too much, there is a concern that the liquidus temperature LT will rise. In addition, when the content of ZrO2 is too little, there is a concern that Pg, F will rise.

[0202] In the optical glass of the second embodiment, the content of Nb2O5 is 12 to 42%. The lower limit of the content of Nb2O5 is preferably 14%, and more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24%, and 25% in the following order. In addition, the upper limit of the content of Nb2O5 is preferably 40%, and more preferably 38%, 36%, 34%, 33%, 32%, 31%, and 30% in the following order. Nb2O5 is a component that helps to achieve both high dispersion and low Pg, F. When the content of Nb2O5 is too much, there is a concern that the stability during reheating is reduced, and there is a concern that the solubility is reduced. When the content of Nb2O5 is too little, there is a concern that low dispersion is achieved.

[0203] In the optical glass of the second embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, and more preferably 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1.70 in the following order. In addition, the lower limit of the mass ratio is preferably 1.00, and more preferably 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40 in the following order. By setting the mass ratio to the above range, the Abbe number νd can be controlled to a desired range. If the mass ratio is too large, the Abbe number νd may exceed the desired range. If the mass ratio is too small, the stability during reheating may be reduced.

[0204] In the optical glass of the second embodiment, the mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, and further preferably 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 in the following order. In addition, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio to the above range, the Pg,F of the glass can be reduced. When the mass ratio is too small, there is a concern that ΔPg,F represented by formula [8] will increase.

[0205] In the optical glass of the second embodiment, the total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3, and Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, and more preferably 95%, 96%, 97%, 98%, and 99% in the following order. In addition, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, there is a concern that the coloring of the glass increases, and there is a concern that the desired optical constants cannot be obtained, the stability during reheating, etc. deteriorates, and there is also a concern that the cost of raw materials for the glass increases.

[0206] In the optical glass of the second embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less. The upper limit of the mass ratio is preferably 5.30, and further preferably 5.20, 5.10, 5.00, 4.90, 4.80, 4.70, 4.50, 4.40, 4.30, 4.20, 4.10, 4.00 in the following order. In addition, the lower limit of the mass ratio is preferably 2.00, and further preferably 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40, 3.50 in the following order. By setting the mass ratio to the above range, it is possible to take into account both low Pg, F and improved stability during reheating. When the mass ratio is too large, there is a concern that Pg, F will rise. If the mass ratio is too small, the stability during reheating may be reduced.

[0207] In the optical glass of the second embodiment, the mass ratio of the content of B2O3 to the content of SiO2 [B2O3 / SiO2] is 0.240 or less. The upper limit of the mass ratio is preferably 0.238, and more preferably 0.236, 0.234, 0.232, 0.230 in the following order. The lower limit of the mass ratio is preferably 0.020, and more preferably 0.030, 0.040, 0.050, 0.060 in the following order. By setting the mass ratio to the above range, the specific gravity can be reduced and the transmittance can be increased. When the mass ratio is too large, there is a concern that the transmittance will deteriorate.

[0208] In the optical glass of the second embodiment, the upper limit of the mass ratio [B2O3 / ZrO2] of the content of B2O3 to the content of ZrO2 is preferably 1.05, and more preferably 1.00, 0.95, 0.90, 0.85, 0.80, and 0.75 in the following order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, and 0.20 in the following order. By setting the mass ratio to the above range, Pg, F can be reduced.

[0209] In the optical glass of the second embodiment, the upper limit of the mass ratio [Na2O / R2O] of the content of Na2O to the total content R2O of Li2O, Na2O and K2O is preferably 0.80, and more preferably 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66, 0.65 in the following order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed.

[0210] In the optical glass of the second embodiment, the upper limit of the total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] is preferably 1.30, and more preferably 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00 in the following order. The lower limit of the total is preferably 0.30, and more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in the following order. By setting the total in the above range, a decrease in stability during reheating can be suppressed.

[0211] In the optical glass of the second embodiment, the upper limit of the mass ratio [R2O / ZrO2] of the total content of Li2O, Na2O and K2O to the content of ZrO2 is preferably 2.00, and more preferably 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1.66, 1.64, 1.62, 1.60 in the following order. The lower limit of the mass ratio is preferably 1.00, and more preferably 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed, and the increase in Pg, F can be suppressed.

[0212] In the optical glass of the second embodiment, the contents and ratios of the glass components other than those described above can be the same as those of the first embodiment.

[0213] In addition, in the optical glass of the second embodiment, the glass properties other than those described above can be the same as those of the first embodiment.

[0214] In addition, the production of the optical glass and the production of the optical element and the like according to the second embodiment may be the same as those of the first embodiment.

[0215] Third Embodiment

[0216] The Abbe number νd of the optical glass of the third embodiment is 36.40 or more.

[0217] The content of SiO2 is 25-55%,

[0218] The content of B2O3 is less than 13%,

[0219] The content of Li2O is less than 20%,

[0220] The content of Na2O is less than 17%,

[0221] The content of ZrO2 is 2-22%,

[0222] The content of Nb2O5 is 12-42%,

[0223] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less,

[0224] The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content R2O of Li2O, Na2O and K2O and the total content RO of MgO, CaO, SrO, BaO and ZnO [R2O / (R2O+RO)] is 0.60 or more,

[0225] The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more,

[0226] The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less,

[0227] The mass ratio of the content of B2O3 to the content of ZrO2 [B2O3 / ZrO2] is 1.05 or less.

[0228] In the optical glass of the third embodiment, the Abbe number νd is 36.40 or more. The Abbe number νd may be 36.50 to 45.00, 36.60 to 43.00, 36.70 to 41.00, 36.80 to 40.00, or 36.90 to 39.50.

[0229] The Abbe number νd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components with relatively low Abbe number νd, i.e., highly dispersed components, include Nb2O5, TiO2, ZrO2, WO3, Bi2O3, Ta2O5, etc. On the other hand, components with relatively high Abbe number νd, i.e., low dispersed components, include SiO2, B2O3, Li2O, Na2O, K2O, La2O3, BaO, CaO, SrO, etc.

[0230] In the optical glass of the third embodiment, the content of SiO2 is 25-55%. The lower limit of the content of SiO2 is preferably 27%, and more preferably 29%, 30%, 31%, 32%, and 33% in the following order. In addition, the upper limit of the content of SiO2 is preferably 53%, and more preferably 50%, 48%, 46%, 44%, 42%, 40%, and 38% in the following order. SiO2 is a network-forming component of glass. When the content of SiO2 is too little, there is a concern that the stability during reheating is reduced. In addition, when the content of SiO2 is too much, there is a concern that the high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases.

[0231] In the optical glass of the third embodiment, the content of B2O3 is 13% or less. The upper limit of the content of B2O3 is preferably 12%, and more preferably 11%, 10%, 9%, and 8% in the following order. In addition, the lower limit of the content of B2O3 is preferably 0%, and more preferably 1%, 2%, and 3% in the following order. The content of B2O3 may also be 0%. B2O3 is a network-forming component of glass. When the content of B2O3 is too much, there is a concern that high dispersibility is impaired, it is difficult to obtain the desired optical constants, and the relative partial dispersion Pg,F increases. When the content of B2O3 is too little, there is a concern that stability during reheating is reduced.

[0232] In the glass of the third embodiment, the content of Li2O is 20% or less. The upper limit of the content of Li2O is preferably 18%, and more preferably 17%, 16%, 15%, 14%, 13%, and 12% in the following order. In addition, the lower limit of the content of Li2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 8% in the following order. Li2O is a component that contributes to low viscosity and low Pg, F of glass. When the content of Li2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Li2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0233] In the glass of the third embodiment, the content of Na2O is 17% or less. The upper limit of the content of Na2O is preferably 16%, and more preferably 15%, 14%, 13%, 12%, 11%, 10%, and 9% in the following order. The lower limit of the content of Na2O is preferably 0%, and more preferably 1%, 2%, 3%, 4%, and 5% in the following order. The content of Na2O may also be 0%. Na2O, like Li2O, is a component that contributes to low viscosity and low Pg, F of glass. When the content of Na2O is too much, there is a concern that the stability during reheating is reduced. In addition, when the content of Na2O is too little, there is a concern that the viscosity of the glass increases and Pg, F increases.

[0234] In the glass of the third embodiment, the content of ZrO2 is 2 to 22%. The lower limit of the content of ZrO2 is preferably 4%, and more preferably 5%, 6%, 7%, 8%, and 9% in the following order. In addition, the upper limit of the content of ZrO2 is preferably 20%, and more preferably 18%, 16%, 15%, 14%, and 13% in the following order. ZrO2 is a component that contributes to low Pg, F. When the content of ZrO2 is too much, there is a concern that the liquidus temperature LT will rise. In addition, when the content of ZrO2 is too little, there is a concern that Pg, F will rise.

[0235] In the optical glass of the third embodiment, the content of Nb2O5 is 12 to 42%. The lower limit of the content of Nb2O5 is preferably 14%, and more preferably 16%, 18%, 20%, 21%, 22%, 23%, 24%, and 25% in the following order. In addition, the upper limit of the content of Nb2O5 is preferably 40%, and more preferably 38%, 36%, 34%, 33%, 32%, 31%, and 30% in the following order. Nb2O5 is a component that helps to achieve both high dispersion and low Pg, F. When the content of Nb2O5 is too much, there is a concern that the stability during reheating is reduced, and there is a concern that the solubility is reduced. When the content of Nb2O5 is too little, there is a concern that low dispersion is achieved.

[0236] In the optical glass of the third embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 2.00 or less. The upper limit of the mass ratio is preferably 1.95, and more preferably 1.90, 1.85, 1.80, 1.75, 1.74, 1.73, 1.72, 1.71, 1.70 in the following order. In addition, the lower limit of the mass ratio is preferably 1.00, and more preferably 1.10, 1.20, 1.25, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40 in the following order. By setting the mass ratio to the above range, the Abbe number νd can be controlled to a desired range. If the mass ratio is too large, the Abbe number νd may exceed the desired range. If the mass ratio is too small, the stability during reheating may be reduced.

[0237] In the optical glass of the third embodiment, the mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more. The lower limit of the mass ratio is preferably 0.62, and further preferably 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 in the following order. In addition, the upper limit of the mass ratio is preferably 1, and the mass ratio is more preferably 1. By setting the mass ratio to the above range, the Pg,F of the glass can be reduced. When the mass ratio is too small, there is a concern that ΔPg,F represented by formula [8] will increase.

[0238] In the optical glass of the third embodiment, the total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% or more. The lower limit of the total content is preferably 94%, and more preferably 95%, 96%, 97%, 98%, 99% in the following order. In addition, the upper limit of the total content is preferably 100%, and the total content is more preferably 100%. If the total content is too small, there is a concern that the coloring of the glass increases, and there is a concern that the desired optical constants cannot be obtained, the stability during reheating, etc. deteriorates, and there is also a concern that the raw material cost of the glass increases.

[0239] In the optical glass of the third embodiment, the mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less. The upper limit of the mass ratio is preferably 5.30, and more preferably 5.20, 5.10, 5.00, 4.90, 4.80, 4.70, 4.50, 4.40, 4.30, 4.20, 4.10, 4.00 in the following order. In addition, the lower limit of the mass ratio is preferably 2.00, and more preferably 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.30, 3.40, 3.50 in the following order. By setting the mass ratio to the above range, it is possible to take into account both low Pg, F and improved stability during reheating. When the mass ratio is too large, there is a concern that Pg, F will rise. If the mass ratio is too small, the stability during reheating may be reduced.

[0240] In the optical glass of the third embodiment, the mass ratio of the content of B2O3 to the content of ZrO2 [B2O3 / ZrO2] is less than 1.05. The upper limit of the mass ratio is further preferably 1.00, 0.95, 0.90, 0.85, 0.80, 0.75 in the following order. The lower limit of the mass ratio is preferably 0.00, and is further more preferably 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20 in the following order. By setting the mass ratio to the above range, Pg, F can be reduced. When the mass ratio is too large, there is a concern that Pg, F increases. In addition, when the mass ratio is too small, there is a concern that the stability during reheating is reduced.

[0241] In the optical glass of the third embodiment, the upper limit of the mass ratio [B2O3 / SiO2] of the content of B2O3 to the content of SiO2 is preferably 0.240, and more preferably 0.238, 0.236, 0.234, 0.232, 0.230 in the following order. The lower limit of the mass ratio is preferably 0.020, and more preferably 0.030, 0.040, 0.050, 0.060 in the following order. By setting the mass ratio to the above range, the specific gravity can be reduced and the transmittance can be increased.

[0242] In the optical glass of the third embodiment, the upper limit of the mass ratio [Na2O / R2O] of the content of Na2O to the total content R2O of Li2O, Na2O and K2O is preferably 0.80, and more preferably 0.79, 0.78, 0.77, 0.76, 0.75, 0.70, 0.69, 0.68, 0.67, 0.66, 0.65 in the following order. The lower limit of the mass ratio is preferably 0.00, and more preferably 0.05, 0.10, 0.15, 0.20, 0.25 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed.

[0243] In the optical glass of the third embodiment, the upper limit of the total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] is preferably 1.30, and more preferably 1.28, 1.26, 1.24, 1.22, 1.20, 1.18, 1.16, 1.14, 1.12, 1.10, 1.08, 1.06, 1.04, 1.02, 1.00 in the following order. The lower limit of the total is preferably 0.30, and more preferably 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65 in the following order. By setting the total in the above range, a decrease in stability during reheating can be suppressed.

[0244] In the optical glass of the third embodiment, the upper limit of the mass ratio [R2O / ZrO2] of the total content of Li2O, Na2O and K2O to the content of ZrO2 is preferably 2.00, and further preferably 1.95, 1.90, 1.85, 1.80, 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, 1.66, 1.64, 1.62, 1.60 in the following order. The lower limit of the mass ratio is preferably 1.00, and further preferably 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45 in the following order. By setting the mass ratio to the above range, the decrease in stability during reheating can be suppressed, and the increase in Pg, F can be suppressed.

[0245] In the optical glass of the third embodiment, the contents and ratios of the glass components other than those described above can be the same as those of the first embodiment.

[0246] In addition, in the optical glass of the third embodiment, the glass properties other than those described above can be the same as those of the first embodiment.

[0247] In addition, the production of the optical glass and the production of the optical element and the like according to the third embodiment may be the same as those of the first embodiment.

[0248] Example

[0249] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the embodiments shown in the examples.

[0250] (Example 1)

[0251] Glass samples having the glass compositions shown in Table 1 were prepared in the following procedure, and various evaluations were performed.

[0252] [Manufacture of optical glass]

[0253] First, prepare oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass as raw materials, weigh the raw materials so that the glass composition of the obtained optical glass is the composition shown in Table 1, and mix the raw materials thoroughly. The prepared raw materials (batch raw materials) thus obtained are put into a platinum crucible, heated at 1350°C to 1400°C for 2 to 4 hours to form molten glass, stirred for homogenization, and after clarification, the molten glass is cast into a mold preheated to an appropriate temperature. The cast glass is heat treated for 30 minutes at any temperature between Tg and a temperature 100°C lower than the glass transition temperature Tg, and naturally cooled to room temperature in the furnace to obtain a glass sample.

[0254] [Confirmation of glass composition]

[0255] The content of each glass component of the obtained glass sample was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and it was confirmed that the content was consistent with the compositions shown in Table 1.

[0256] [Reheating test (stability during reheating)]

[0257] The obtained glass sample was cut into a size of 1 cm×1 cm×1 cm, and heated for 10 minutes in a first test furnace set at the glass transition temperature Tg of the glass sample, and further heated for 10 minutes in a second test furnace set at a temperature 220°C higher than the glass transition temperature Tg. Then, the presence or absence of crystals was confirmed by an optical microscope (observation magnification: 40 to 100 times). The number of crystals (number of foreign matter) per 1g was measured.

[0258] [Measurement of optical properties]

[0259] The obtained glass sample was further annealed for about 30 minutes to about 2 hours near the glass transition temperature Tg, and then cooled to room temperature in a furnace at a temperature drop rate of -30°C / hour to obtain an annealed sample. The refractive index, Abbe number νd, relative partial dispersion Pg,F, specific gravity, glass transition temperature Tg, λ80 and λ5 of the obtained annealed sample were measured, and the results are shown in Table 1.

[0260] (i) Refractive index and Abbe number νd and relative partial dispersion Pg,F

[0261] The refractive index of the annealed sample was measured at 12 wavelengths shown in Table A according to Japanese Industrial Standard (JIS Standard) JIS B 7071-1 Methods for measuring the refractive index of optical glass - Part 1: Minimum deviation angle method.

[0262] Next, the refractive index of each ray obtained by the measurement is substituted into the Schott dispersion formula specified in Appendix B of the Japanese Industrial Standard (JIS Standard) JIS B7071-1 Optical Glass Refractive Index Measurement Method - Part 1: Minimum Deviation Angle Method, and the constant of the Schott dispersion formula is obtained by the least square method. Then, using the Schott dispersion formula with the determined constant, the Abbe number νd and the relative partial dispersion Pg, F are calculated.

[0263] Table A

[0264] Wavelength (nm) Spectral rays light source 1013.98 T-ray (infrared mercury) Hg 852.11 S-ray (infrared cesium) Cs 706.52 R-rays (red helium) He 656.27 C rays (red hydrogen) H 643.85 C′ rays (red cadmium) Cd 587.56 d-rays (yellow helium) He 546.07 e-ray (green mercury) Hg 486.13 F rays (blue hydrogen) H 479.99 F' rays (blue cadmium) Cd 435.84 g-rays (blue mercury) Hg 404.66 H-rays (purple mercury) Hg 365.01 I-ray (ultraviolet mercury) Hg

[0265] Schott distributed: n 2 =a0+a1λ 2 +a2λ- 2 +a3λ -4 +a4λ -6 +a5λ -8

[0266] Where n is the refractive index, λ is the wavelength (μm), and a0, a1, a2, a3, a4, and a5 are constants.

[0267] It should be noted that the refractive index nd refers to the refractive index at a wavelength of 587.56 nm.

[0268] (ii) Specific gravity

[0269] The specific gravity was measured by the Archimedean method.

[0270] (iii) Glass transition temperature Tg

[0271] The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN CO., LTD. at a heating rate of 10° C. / min.

[0272] (iv)λ80、λ5

[0273] The annealed sample was processed into a thickness of 10 mm and parallel to each other and optically polished planes, and the spectral transmittance in the wavelength range of 280 nm to 700 nm was measured. The intensity of the light incident vertically on one optically polished plane was set as intensity A, and the intensity of the light emitted from the other plane was set as intensity B, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance is 80% is set as λ80, and the wavelength at which the spectral transmittance is 5% is set as λ5. It should be noted that the spectral transmittance also includes the reflection loss of the light on the sample surface.

[0274]

[0275] (Example 2)

[0276] Using each optical glass produced in Example 1, lens blanks were produced by a known method, and the lens blanks were processed by a known method such as grinding to produce various lenses.

[0277] The optical lenses produced include various lenses such as biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses.

[0278] Various lenses can be combined with lenses made of other types of optical glass to satisfactorily correct secondary chromatic aberration.

[0279] In addition, since the specific gravity of glass is relatively low, each lens is lighter than a lens having the same optical characteristics and size, and can be used in various imaging devices, especially in autofocus imaging devices for reasons of energy saving. Similarly, prisms were made using various optical glasses made in Example 1.

[0280] It should be understood that the embodiments disclosed herein are all exemplary and do not constitute limitations. The scope of the present invention is defined by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0281] For example, by adjusting the composition described in the specification to the glass composition exemplified above, the optical glass of one embodiment of the present invention can be produced.

[0282] Furthermore, it is of course possible to arbitrarily combine two or more of the items exemplified or described as the preferred range in the specification.

Claims

1. An optical glass having an Abbe number νd of 36.40 or more, The content of SiO2 is 25-55% by mass. The content of B2O3 is 13% by mass or less, The content of Li2O is 20 mass % or less, The content of Na2O is 17% by mass or less, The content of ZrO2 is 2 to 22% by mass. The content of Nb2O5 is 12 to 42% by mass. The content of BaO is 5.0 mass % or less, The total content of SiO2, B2O3 and P2O5 [SiO2+B2O3+P2O5] is 38.0% by mass or more, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 1.48 or more and 1.85 or less, The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more, The mass ratio of the total content of Li2O, Na2O and K2O R2O to the content of ZrO2 [R2O / ZrO2] is 2.00 or less, The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is less than 5.

00.

2. An optical glass having an Abbe number νd of 36.40 or more, The content of SiO2 is 25-55% by mass. The content of B2O3 is 13% by mass or less, The content of Li2O is 20 mass % or less, The content of Na2O is 17% by mass or less, The content of ZrO2 is 2 to 22% by mass. The content of Nb2O5 is 12 to 42% by mass. The content of La2O3 is 7.0 mass % or less, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 1.0 or more and 1.85 or less, The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more, The mass ratio of the total content of Li2O, Na2O and K2O R2O to the content of ZrO2 [R2O / ZrO2] is 2.00 or less, The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 4.30 or less, The mass ratio of the content of B2O3 to the content of SiO2 [B2O3 / SiO2] is 0.240 or less.

3. An optical glass having an Abbe number νd of 36.40 or more, The content of SiO2 is 25-55% by mass. The content of B2O3 is 13% by mass or less, The content of Li2O is 20 mass % or less, The content of Na2O is 17% by mass or less, The content of ZrO2 is 2 to 22% by mass. The content of Nb2O5 is 12 to 42% by mass. The content of BaO is 5.0 mass % or less, The total content of SiO2, B2O3 and P2O5 [SiO2+B2O3+P2O5] is 38.0% by mass or more, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the total content of Nb2O5, TiO2, Bi2O3, WO3 and Ta2O5 [(SiO2+B2O3+P2O5) / (Nb2O5+TiO2+Bi2O3+WO3+Ta2O5)] is 1.48 or more and 1.85 or less, The mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content RO of MgO, CaO, SrO, BaO and ZnO and the total content R2O [R2O / (R2O+RO)] is 0.60 or more, The mass ratio of the total content of Li2O, Na2O and K2O R2O to the content of ZrO2 [R2O / ZrO2] is 2.00 or less, The total content of SiO2, B2O3, P2O5, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, TiO2, Nb2O5, WO3, ZrO2, La2O3, Gd2O3 and Y2O3 is 93% by mass or more, The mass ratio of the total content of SiO2, B2O3 and P2O5 to the content of ZrO2 [(SiO2+B2O3+P2O5) / ZrO2] is 5.45 or less, The mass ratio of the content of B2O3 to the content of ZrO2 [B2O3 / ZrO2] is 1.05 or less.

4. The optical glass according to any one of claims 1 to 3, wherein The mass ratio of the content of Na2O to the total content of R2O of Li2O, Na2O and K2O [Na2O / R2O] is 0.80 or less.

5. The optical glass according to any one of claims 1 to 3, wherein The total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the total mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] are less than 1.

30.

6. The optical glass according to claim 4, wherein: The total mass ratio of the total content R2O of Li2O, Na2O and K2O to the total content of SiO2, B2O3 and P2O5, and the total mass ratio of the content of Na2O to the total content R2O of Li2O, Na2O and K2O [{R2O / (SiO2+B2O3+P2O5)}+(Na2O / R2O)] are less than 1.

30.

7. An optical element made of the optical glass according to any one of claims 1 to 6.

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