TW202417391A - Optical glass and optical element - Google Patents

Abstract

Provided is an optical glass having a low glass transition temperature and a refractive index and an Abbe number satisfying a predetermined formula. In the glass composition of the optical glass, the content of Li2O exceeds 0 mass%, the content of B2O3 is from 3.00 mass% to 30.00 mass% (inclusive), the content of SiO2 exceeds 0 mass% to 8.00 mass% (inclusive), the content of La2O3 is from 15.00 mass% to 55.00 mass% (inclusive), the content of ZnO is from 3.00 mass% to 30.00 mass% (inclusive), and the content of TiO2 is 0.60 mass% (inclusive). The total content of Li2O and ZnO (Li2O + ZnO) is more than 10.20 mass%, the mass ratio of the content of B2O3 to the content of Li2O (B2O3/Li2O) is more than 5.00 and less than 21.00, the mass ratio of the content of SiO2 to the content of Li2O (SiO2/Li2O) is less than 10.00, the glass transition temperature Tg of the optical glass is less than 610 DEG C, the liquid phase temperature LT is more than 1090 DEG C, the refractive index nd and the glass transition temperature Tg satisfy the following formula (1), and the refractive index nd and the Abbe number [nu]d satisfy the following formula (2). Formula (1): Tg < 2500 * nd-4050; formula (2): [nu]d > -88.355 * nd + 201.

Description

Optical glass and optical components

The present invention relates to optical glass and optical components.

In recent years, various optical glasses have been proposed as materials for optical elements (see, for example, Patent Document 1). Prior Art Documents Patent Documents

Patent document 1: Japanese Patent Application Publication No. 2008-201661

Problem that the invention aims to solve

Optical glass whose refractive index and Abbe number satisfy a given relationship is useful as a material for optical elements. For example, as a specific example of such a relationship, "Equation (2): νd＞-88.355*nd+201" can be cited.

In addition, one of the properties desired for optical glass is a low glass transition temperature Tg. Low Tg glass is preferred because, for example, it is well suited for precision pressing.

An embodiment of the present invention aims to provide an optical glass having a refractive index and an Abbe number satisfying the above formula (2) and a low glass transition temperature. Solution to the problem

One embodiment of the present invention is an optical glass, wherein, in a glass composition expressed in mass%, a Li ₂ O content exceeds 0 mass%, a B ₂ O ₃ content is 3.00 mass% or more and 30.00 mass% or less, a SiO ₂ content exceeds 0 mass% and is 8.00 mass% or less, a La ₂ O ₃ content is 15.00 mass% or more and 55.00 mass% or less, a ZnO content is 3.00 mass% or more and 30.00 mass% or less, a TiO ₂ content is 0.60 mass% or less, a total content of Li ₂ O and ZnO (Li ₂ O+ZnO) is 10.20 mass% or more, a mass ratio of the B ₂ O ₃ content to the Li ₂ O content (B ₂ O ₃ /Li ₂ O) is 5.00 or more and 21.00 or less, and a SiO ₂ content relative to the Li ₂ The mass ratio of O content (SiO ₂ /Li ₂ O) is 10.00 or less, the glass transition temperature Tg of the optical glass is less than 610°C, the liquidus temperature LT is 1090°C or more, the refractive index nd and the glass transition temperature Tg satisfy the following formula (1), and the refractive index nd and the Abbe number νd satisfy the following formula (2), Formula (1): Tg＜2500*nd-4050 Formula (2): νd＞-88.355*nd+201. Effects of the invention

According to one embodiment of the present invention, an optical glass having a low glass transition temperature and optical constants useful as a material for an optical element can be provided. In addition, according to one embodiment of the present invention, an optical element made of such an optical glass can be provided.

[Optical glass] In the present invention and this specification, the glass composition of optical glass is described by mass %, cation % or molar % expression.

In the glass composition expressed in mass % and the glass composition expressed in mole %, the glass composition is expressed in terms of oxide-based glass composition. Here, "oxide-based glass composition" refers to a glass composition obtained by converting the substances that are completely decomposed when the glass raw materials are melted and exist in the glass in the form of oxides. In the glass composition expressed in mass %, the glass composition is expressed in terms of mass basis (mass %, mass ratio). Hereinafter, with respect to the glass composition expressed in mass %, "mass %" is also simply described as "%". In the glass composition expressed in mole %, the glass composition is expressed in terms of mole basis (mole %, mole ratio). Hereinafter, with respect to the glass composition expressed in mole %, "mole %" is also simply described as "%".

Regarding glass compositions expressed in cation % , the content and total content of cation components are expressed in cation %. Here, "cation %" is a value calculated as "(number of cations of concern/total number of cations in glass components) × 100", which represents the molar percentage of the amount of cations of concern relative to the total amount of cation components. Hereinafter, regarding glass compositions expressed in cation % , "cation %" will also be simply expressed as "%". The cation ratio is the molar ratio of the contents of cation components to each other, and is equal to the ratio of the contents of the cation components of concern expressed in cation %. Regarding cationic components, for example, when expressing them as Li ⁺ and Si ⁴⁺ , the valence of the cationic components (for example, the valence of Li ⁺ is +1, and the valence of Si ⁴⁺ is +4) is a value determined by convention, which is the same as expressing Li, Si, etc. as Li ₂ O, SiO ₂ , etc. on an oxide basis. Regarding components expressed as _{Am On} (A represents a cation, O represents oxygen, and m and n are integers determined by a stoichiometric method) on an oxide basis, the cation A is expressed as ^As+ . Here, s=2n/m. Therefore, when analyzing and quantifying glass compositions, for example, the valence of the cationic components does not need to be analyzed.

In the present invention and this specification, the content of a constituent is 0%, 0.0% or 0.00%, or is not contained or not introduced, which means that the constituent is not substantially contained, and means that the content of the constituent is below the level of impurities. Below the level of impurities means, for example, less than 0.01%. "0%" can mean, for example, "0.0%" or "0.00%".

The glass composition in the present invention and the specification can be obtained by methods such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). For example, quantitative analysis is performed on each element separately using ICP-AES. Then, the analysis value is converted into an oxide expression. The analysis value based on ICP-AES sometimes includes a measurement error of, for example, about ±5% of the analysis value. Therefore, the value expressed in oxides converted from the analysis value sometimes also includes an error of about ±5%.

As for the results of quantitative analysis of glass composition, the composition expressed in mass % on an oxide basis can be converted into a glass composition expressed in cation % by, for example, the method described below. When the glass contains N glass components, the kth glass component is expressed as A(k) _m O _n . Here, k is an arbitrary integer greater than 1 and less than N. A(k) is a cation, O is oxygen, and m and n are integers that can be determined by a chemometric method. For example, in the case of B ₂ O ₃ expressed on an oxide basis, m=2 and n=3, and in the case of SiO ₂ , m=1 and n=2. Next, the content of A(k) _m O _n is denoted as X(k) [mass %]. Here, when the atomic weight of A(k) is P(k) and the atomic number of oxygen O is Q, the formal molecular weight R(k) of A(k) _m O _n is R(k) = P(k) × m + Q × n. Furthermore, when B = 100/{Σ[m×X(k)/R(k)]}, the content (cation %) of the cationic component A(k) ^s+ is [X(k)/R(k)]×m×B(cation %). Here, Σ represents the sum of m×X(k)/R(K) for k=1 to N. m varies depending on k. s is 2n/m. In addition, for the molecular weight R(k), the fourth decimal place is rounded off and the value expressed to the third decimal place can be used for calculation. In addition, regarding several glass components and additives, molecular weights expressed on the basis of oxides are shown in the following Table 1.

In the present invention and this specification, the refractive index refers to the refractive index nd under helium d-ray (wavelength 587.56 nm).

In the present invention and this specification, the Abbe number νd is used as a value representing properties related to dispersion, and is represented by the following mathematical formula. νd = (nd-1)/(nF-nC) In the above formula, nF is the refractive index under blue hydrogen F rays (wavelength 486.13nm), and nC is the refractive index under red hydrogen C rays (656.27nm).

Hereinafter, the above-mentioned optical glass (sometimes simply referred to as "glass") will be described in more detail.

<Glass Composition> (Li ₂ O, Li ⁺ ) Li (Li ₂ O in a glass composition expressed in mass % or mole % and Li ⁺ in a glass composition expressed in cation %) is a component capable of suppressing a decrease in the refractive index and lowering the glass transition temperature, and therefore must be contained in the above optical glass.

In the glass composition expressed in mass %, the _Li2O content exceeds 0%, preferably 0.20% or more, and is further preferably 0.30% or more, 0.40% or more, 0.45% or more, 0.50% or more, 0.55% or more, 0.60% or more, 0.62% or more, 0.64% or more, 0.66% or more, 0.68% or more, 0.70% or more, 0.72% or more, 0.74% or more, 0.76% or more, 0.77% or more, 0.78% or more, 0.79% or more, 0.80% or more, 0.81% or more, 0.82% or more, and 0.83% or more. The upper limit of the _Li2O content is not particularly limited, and may be, for example, 1.80% or less, preferably 1.70% or less, and more preferably 1.60% or less, 1.55% or less, 1.50% or less, 1.48% or less, 1.46% or less, 1.44% or less, 1.42% or less, 1.40% or less, 1.38% or less, 1.36% or less, 1.34% or less, 1.32% or less, and 1.31% or less, in this order.

In the glass composition expressed as cation %, the Li ⁺ content exceeds 0%, preferably 0.50% or more, and is further preferably in the order of 1.00% or more, 1.50% or more, 2.00% or more, 2.50% or more, 3.00% or more, 3.25% or more, 3.50% or more, 3.75% or more, 4.00% or more, 4.25% or more, 4.50% or more, 4.75% or more, and 5.00% or more. The upper limit of the Li ⁺ content is not particularly limited, and can be, for example, 12.00% or less, preferably 11.00% or less, and preferably 10.50% or less, 10.00% or less, 9.75% or less, 9.50% or less, 9.25% or less, 9.00% or less, 8.75% or less, 8.50% or less, 8.25% or less, and 8.00% or less, in this order.

In the glass composition expressed in mole %, the Li ₂ O content exceeds 0%, preferably 0.50% or more, and more preferably in the order of 1.00% or more, 1.50% or more, 2.00% or more, 2.50% or more, 3.00% or more, 3.10% or more, 3.30% or more, 3.50% or more, 3.70% or more, and 3.91% or more. The upper limit of the Li ₂ O content is not particularly limited, and for example, it may be 11.00% or less, preferably 10.00% or less, and more preferably in the order of 9.50% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.30% or less, 7.10% or less, 6.90% or less, 6.70% or less, and 6.51% or less.

(B ₂ O ₃ ) B ₂ O ₃ is a network-forming component and a component that contributes to maintaining the thermal stability and melting property of glass. Therefore, in the glass composition expressed in mass%, the B ₂ O ₃ content is 3.00% or more, preferably 5.00% or more, and more preferably 6.00% or more, 7.00% or more, 8.00% or more, 8.50% or more, 9.00% or more, 9.50% or more, 10.00% or more, 10.50% or more, and 10.83% or more. B ₂ O ₃ is also a component that lowers the refractive index of glass when contained in a large amount. Therefore, in the glass composition expressed in mass %, _{the B2O3} content is 30.00% or less, preferably 29.00% or less, and further preferably 28.00% or less, 27.00% or less, 26.00% or less, 25.00% or less, 24.00% or less, 23.00% or less, 22.00% or less, 21.00% or less, 20.00% or less, 19.00% or less, 18.00% or less, 17.00% or less, 16.00% or less, 15.50% or less, 15.00% or less, 14.50% or less, 14.00% or less, and 13.78% or less, in this order.

(SiO ₂ ) SiO ₂ is also a network-forming component and a component that helps maintain the thermal stability and solubility of glass. From this point of view, in the glass composition expressed in mass %, the SiO ₂ content exceeds 0%, preferably 0.50% or more, and more preferably 1.00% or more, 1.50% or more, 2.00% or more, 2.25% or more, 2.50% or more, 2.75% or more, 2.80% or more, 2.85% or more, 2.90% or more, 2.95% or more, 3.00% or more, 3.02% or more, 3.04% or more, and 3.06% or more. SiO ₂ is also a component that causes a low refractive index of glass when contained in a large amount. Therefore, in the glass composition expressed in mass %, the _SiO2 content is 8.00% or less, preferably 7.50% or less, more preferably 7.00% or less, and further preferably 6.75% or less, 6.50% or less, 6.25% or less, 6.00% or less, 5.75% or less, and 5.60% or less, in this order.

(B ₂ O ₃ /Li ₂ O) In the glass composition expressed in mass %, the mass ratio of the B ₂ O ₃ content to the Li ₂ O content (B ₂ O ₃ /Li ₂ O) is 5.00 or more, preferably 5.50 or more, and more preferably 6.00 or more, 6.20 or more, 6.40 or more, 6.60 or more, 6.80 or more, 7.00 or more, 7.20 or more, 7.40 or more, 7.60 or more, 7.80 or more, 8.00 or more, 8.25 or more, and 8.36 or more, in this order. The upper limit is 21.00 or less, preferably 20.00 or less, and more preferably 19.50 or less, 19.00 or less, 18.50 or less, 18.00 or less, 17.75 or less, 17.50 or less, 17.25 or less, 17.00 or less, 16.75 or less, and 16.54 or less. The mass ratio (B ₂ O ₃ /Li ₂ O) is preferably the upper limit mentioned above from the viewpoint of lowering the glass transition temperature, and is preferably the lower limit mentioned above from the viewpoint of suppressing the increase in the glass transition temperature and maintaining thermal stability.

In the glass composition expressed as cation %, the cation ratio of the B ³⁺ content to the Li ⁺ content (B ³⁺ /Li ⁺ ) is preferably 1.50 or more, more preferably 2.00 or more, 2.25 or more, 2.50 or more, 2.75 or more, 3.00 or more, 3.25 or more, 3.50 or more, and 3.58 or more. The upper limit is preferably 9.50 or less, and more preferably 9.00 or less, 8.80 or less, 8.60 or less, 8.40 or less, 8.20 or less, 8.00 or less, 7.80 or less, 7.60 or less, 7.40 or less, 7.20 or less, and 7.10 or less.

(B ³⁺ /Si ⁴⁺ ) In the glass composition expressed as cation %, the cation ratio of B ³⁺ content to Si ⁴⁺ content (B ³⁺ /Si ⁴⁺ ) is preferably above 1.25, and is further preferably above 1.50, above 1.75, above 2.00, above 2.25, above 2.50, above 2.75, above 3.00, above 3.10, above 3.20, above 3.30, above 3.40, and above 3.50, in the order of above. In addition, the cation ratio (B ³⁺ /Si ⁴⁺ ) is preferably 11.00 or less, and is more preferably in the order of 10.50 or less, 10.00 or less, 9.75 or less, 9.50 or less, 9.25 or less, 9.00 or less, 8.75 or less, 8.50 or less, 8.25 or less, 8.00 or less, 7.75 or less, 7.60 or less, 7.50 or less, 7.40 or less, and 7.30 or less. From the viewpoint of maintaining the thermal stability of the glass and the high refractive index characteristics, the cation ratio (B ³⁺ /Si ^{4 +} ) is preferably within the above range.

In the glass composition expressed in mass %, the mass ratio of the B ₂ O ₃ content to the SiO ₂ content (B ₂ O ₃ /SiO ₂ ) is preferably 0.25% or more, more preferably 0.50 or more, 0.75 or more, 1.00 or more, 1.20 or more, 1.40 or more, 1.60 or more, 1.70 or more, 1.80 or more, 1.90 or more, 2.00 or more, and 2.02 or more. The upper limit is preferably 9.00 or less, and more preferably 8.50 or less, 8.00 or less, 7.50 or less, 7.00 or less, 6.50 or less, 6.00 or less, 5.75 or less, 5.50 or less, 5.25 or less, 5.00 or less, 4.75 or less, 4.50 or less, and 4.23 or less.

(SiO ₂ /Li ₂ O) In the glass composition expressed in mass %, the mass ratio of the SiO ₂ content to the Li ₂ O content (SiO ₂ /Li ₂ O) is 10.00 or less, preferably 9.00 or less, and more preferably 8.50 or less, 8.00 or less, 7.50 or less, 7.00 or less, 6.75 or less, 6.50 or less, 6.25 or less, 6.00 or less, 5.75 or less, 5.50 or less, 5.25 or less, and 5.18 or less, in this order. The lower limit may exceed 0, preferably 0.40 or more, and more preferably 0.60 or more, 0.80 or more, 1.00 or more, 1.20 or more, 1.40 or more, 1.60 or more, 1.80 or more, 2.00 or more, 2.25 or more, 2.50 or more, and 2.68 or more. The mass ratio (SiO ₂ /Li ₂ O) is preferably the upper limit mentioned above from the viewpoint of lowering the glass transition temperature, and is preferably the lower limit mentioned above from the viewpoint of suppressing the increase in the glass transition temperature and maintaining thermal stability.

In the glass composition expressed as cation %, the cation ratio of Si ⁴⁺ content to Li ⁺ content (Si ⁴⁺ /Li ⁺ ) can be below 2.40, and preferably below 2.30, below 2.20, below 2.10, below 2.00, below 1.90, below 1.80, below 1.70, below 1.65, below 1.60, below 1.55, below 1.50, below 1.48, below 1.46, below 1.44, below 1.42, below 1.40, below 1.38, below 1.36, below 1.34, below 1.32, below 1.30, and below 1.29. Regarding the lower limit, it may exceed 0, and is preferably in the order of 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.50 or more, 0.52 or more, 0.54 or more, 0.56 or more, 0.58 or more, 0.60 or more, 0.62 or more, 0.64 or more, and 0.66 or more.

(Rare earth components) La ₂ O _3: In the glass composition expressed in mass %, the La ₂ O ₃ content is 15.00% or more, preferably 17.00% or more, and more preferably 20.00% or more, 21.00% or more, 22.00% or more, 23.00% or more, 24.00% or more, 25.00% or more, 26.00% or more, 26.50% or more, 27.00% or more, 27.50% or more, 28.00% or more, and 28.35% or more. In the glass composition expressed in mass %, the La ₂ O ₃ content is 55.00% or less, preferably 50.00% or less, and more preferably 47.00% or less, 45.00% or less, 44.00% or less, 43.00% or less, 42.00% or less, 41.00% or less, 40.00% or less, 39.50% or less, 39.00% or less, 38.50% or less, 38.00% or less, 37.50% or less, and 37.22% or less, in this order.

In the glass composition expressed in mass %, _{the Gd 2 O 3 content may} be 0%, 0% _or more, or more than 0%, preferably in the order of 0.00% or more, 0.20% or more, 0.40% or more, 0.60% or more, and 0.80% or more. The upper limit is preferably 15.00% or less, and more preferably in the order of 14.75% or less, 14.50% or less, 14.25% or less, 14.00% or less, 13.85% or less, 13.75% or less, 13.50% or less, 13.25% or less, 13.00% or less, 12.75% or less, 12.55% or less, 12.25% or less, and 12.03% or less.

In the glass composition expressed in mass%, _{the Y2O3} content may be 0%, 0% or more, or _more than 0%. The upper limit is preferably 11.00% or less, and more preferably in the order of 10.50% or _less , 10.00% or less, 9.50% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.04% or less, 6.50% or less, 6.00% or less, and 5.84% or less.

Regarding rare earth components, La, Gd and Y are components that can maintain low dispersibility and increase the refractive index. From the perspective of maintaining or improving thermal stability, the content of each rare earth oxide is preferably within the above range. Compared with Gd, which is also a rare earth component, Y has a smaller effect on increasing the refractive index. In addition, when the total content of rare earth components is excessive, the thermal stability of the glass tends to decrease. Therefore, from the perspective of maintaining thermal stability and maintaining high refractive index characteristics, La and/or Gd are preferably introduced as rare earth components rather than Y.

(Lu ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Lu ₂ O ₃ )) From the viewpoint of maintaining thermal stability, the smaller the proportion of Lu in the total amount of the rare earth components, the better, and more preferably no Lu is contained. From this point of view, in the glass composition expressed in mass %, the mass ratio of Lu ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ (Lu ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Lu ₂ O ₃ )) is preferably less than 0.50, more preferably less than 0.40, less than 0.30, less than 0.20, and less than 0.10 in this order, and further preferably does not contain Lu ³⁺ (therefore, the above mass ratio is zero).

(ZnO) In the glass composition expressed in mass%, the ZnO content is 3.00% or more, preferably 3.50% or more, and preferably 4.00% or more, 4.50% or more, 5.00% or more, 5.25% or more, 5.50% or more, 5.75% or more, 6.00% or more, 6.25% or more, 6.50% or more, 6.75% or more, 7.00% or more, 7.25% or more, 7.53% or more, 7.75% or more, 8.00% or more, 8.25% or more, 8.50% or more, 8.75% or more, 9.00% or more, 9.10% or more, 9.20% or more, and 9.30% or more. The upper limit is 30.00% or less, preferably 27.00% or less, and preferably 25.00% or less, 23.00% or less, 22.00% or less, 21.00% or less, 20.00% or less, 19.50% or less, 19.00% or less, 18.50% or less, 17.00% or less, 16.75% or less, 16.50% or less, 16.25% or less, 16.00% or less, 15.75% or less, and 15.65% or less. Zn is a component that suppresses the decrease in refractive index, lowers the glass transition temperature, and improves solubility. On the other hand, when excessively contained, the liquidus temperature becomes higher and the thermal stability of the glass decreases. From these viewpoints, the ZnO content is preferably within the above range.

(Li ₂ O + ZnO) From the viewpoint of achieving a low Tg, in the glass composition expressed in mass %, the total content of Li ₂ O and ZnO (Li ₂ O + ZnO) is 10.20% or more, preferably 10.22% or more, 10.30% or more, 10.40% or more, and more preferably 10.60% or more, and 10.79% or more. Regarding the upper limit, from the viewpoint of thermal stability of the glass, it is preferably 21.00% or less, and more preferably 20.00% or less, 19.50% or less, 19.00% or less, 18.50% or less, 18.00% or less, 17.75% or less, 17.50% or less, 17.25% or less, 17.00% or less, and 16.79% or less.

(TiO ₂ ) Ti is a component that increases the refractive index and improves dispersion. In addition, if excessive Ti is introduced, it reacts with the molding surface of the molding mold during press molding, tends to deteriorate the surface quality of the glass, and the coloring of the glass sometimes becomes stronger. In addition, from the viewpoint of suppressing the degradation of the release film described later, it is preferred that Ti is not contained or its content is very small. From these viewpoints, in the glass composition expressed in mass %, the TiO ₂ content is 0.60% or less, preferably 0.40% or less, more preferably 0.30% or less, 0.20% or less, 0.10% or less, and even more preferably 0% (i.e., not contained).

(Ta ₂ O ₅ ) Ta is a component that has the function of maintaining high refractive index, low dispersion and thermal stability. Therefore, in the glass composition expressed in mass%, the Ta ₂ O ₅ content is preferably 7.00% or more, and more preferably in the order of 7.50% or more, 8.00% or more, 8.50% or more, 8.75% or more, 9.00% or more, 9.25% or more, 9.50% or more, 9.75% or more, 10.00% or more, 10.25% or more, and 10.43% or more. There is no particular limitation on the upper limit, and for example, it may be 19.00% or less, preferably 18.00% or less, and more preferably 17.50% or less, 17.00% or less, 16.50% or less, 16.00% or less, 15.75% or less, 15.50% or less, 15.25% or less, 15.00% or less, and 14.92% or less, in this order.

(Nb ₂ O ₅ ) Nb is a component that plays a role in increasing the refractive index of glass. When contained in excessive amount, there is a tendency to reduce the thermal stability of glass. In the glass composition expressed in mass %, the Nb ₂ O ₅ content may be 0%, 0% or more, or more than 0%, preferably in the order of 0% or more, 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, and 0.60% or more. As for the upper limit, it is preferably 9.00% or less, and more preferably in the order of 8.00% or less, 7.50% or less, 7.00% or less, 6.50% or less, 6.00% or less, 5.80% or less, 5.60% or less, 5.40% or less, and 5.24% or less.

(ZrO ₂ ) In the glass composition expressed in mass %, the ZrO ₂ content may be 0%, 0% or more, or more than 0%, preferably in the order of 0.00% or more, 0.50% or more, 1.00% or more, 1.20% or more, 1.40% or more, 1.60% or more, 1.80% or more, and 1.90% or more. The upper limit is preferably 10.00% or less, and more preferably in the order of 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.00% or less, 6.80% or less, 6.60% or less, 6.40% or less, 6.20% or less, 6.00% or less, and 5.90% or less. By introducing Zr into glass, the thermal stability of the glass can be improved without lowering the refractive index of the glass, so it is preferred to introduce Zr.

(WO ₃ ) In the glass composition expressed in mass %, the WO ₃ content may be 0%, 0% or more, or more than 0%, preferably in the order of 0% or more, 1.00% or more, 2.00% or more, 2.50% or more, 3.00% or more, 3.50% or more, 4.00% or more, 4.20% or more, 4.40% or more, 4.60% or more, 4.80% or more, and 4.93% or more. The upper limit is preferably 21.00% or less, preferably in the order of 20.00% or less, 19.00% or less, 18.50% or less, 18.00% or less, 17.80% or less, 17.60% or less, 17.40% or less, 17.20% or less, 17.00% or less, 16.80% or less, and 16.66% or less. W is a component that improves the thermal stability and melting property of glass and increases the refractive index. On the other hand, when contained in a large amount, the dispersion becomes high and the suitability for precision pressing decreases, so a smaller amount is preferred.

(Nb ₂ O ₅ +TiO ₂ +WO ₃ )/(SiO ₂ +B ₂ O ₃ ) In the glass composition expressed in mass %, the mass ratio of the total content of Nb ₂ O ₅ , TiO ₂ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ (Nb ₂ O ₅ +TiO ₂ +WO ₃ )/(SiO ₂ +B ₂ O ₃ ) is preferably 0.40 or more, and more preferably 0.45 or more, 0.50 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, 0.60 or more, 0.61 or more, 0.62 or more, and 0.63 or more, in this order. The upper limit is preferably 1.60 or less, and is more preferably 1.40 or less, 1.35 or less, 1.30 or less, 1.28 or less, 1.26 or less, 1.24 or less, 1.22 or less, 1.20 or less, 1.19 or less, 1.18 or less, 1.17 or less, 1.16 or less, 1.15 or less, and 1.14 or less. The mass ratio (Nb ₂ O ₅ +TiO ₂ +WO ₃ )/(SiO ₂ +B ₂ O ₃ ) is preferably the above lower limit from the viewpoint of maintaining the high refractive index characteristics of the glass, and is preferably the above upper limit from the viewpoint of maintaining thermal stability.

(ZnO/WO ₃ ) In the glass composition expressed in mass %, the mass ratio of the ZnO content to the WO ₃ content (ZnO/WO ₃ ) is preferably 0.10 or more, more preferably 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.63 or more, 0.67 or more, 0.70 or more, 0.73 or more, and 0.76 or more. The upper limit is preferably 5.00 or less, and more preferably 4.80 or less, 4.60 or less, 4.40 or less, 4.20 or less, 4.00 or less, 3.80 or less, 3.60 or less, 3.40 or less, 3.20 or less, 3.00 or less, 2.80 or less, 2.60 or less, and 2.46 or less. The mass ratio (ZnO/WO ₃ ) is preferably within the above lower limit from the viewpoint of lowering the glass transition temperature and maintaining low dispersibility, and is preferably within the above upper limit from the viewpoint of maintaining the high refractive index characteristics of the glass.

(Sb ₂ O ₃ ) Sb is a component that functions as a clarifier. From the viewpoint of suppressing damage to the molding surface of the press-molding mold during precision press molding and from the viewpoint of suppressing coloring of the glass, the smaller the amount of Sb 2 O 3 added, the better. Regarding the Sb ₂ O ₃ content, in the glass composition expressed in mass %, the Sb ₂ O ₃ content expressed as an added ratio (the Sb ₂ O ₃ content when the total mass of the glass components other than Sb ₂ O ₃ is 100 mass %) is preferably in the order of 0% or more, 0.01% or more, and 0.02% or more. In addition, it is preferably in the order of 1.00% or less, 0.90% or less, 0.80% or less, 0.70% or less, 0.60% or less, and 0.50% or less.

(Anion component) The above optical glass may be an oxide glass, and may contain ^O2- as an anion component. In the present invention and this specification, the content of anion components in a glass composition expressed by anion % is expressed by anion %. Here, "anion %" refers to a value calculated according to "(the number of anions of concern/the total number of anions in the glass component) × 100", which is the molar percentage of the amount of anions of concern relative to the total amount of anion components. In the glass composition expressed in anion %, the O ^2- content is preferably 95.0 anion % or more, and is more preferably 97.0 anion % or more, 98.0 anion % or more, 99.0 anion % or more, 99.5 anion % or more, and 100 anion % or more. From the viewpoint of easy volatility when the glass is melted, the ^F- content is preferably 0.1 anion % or less, and more preferably 0 anion % (i.e., F is not included). The results of quantitative analysis of the glass composition, the composition expressed in mass % according to the oxide basis, can be converted into the glass composition expressed in anion % by, for example, the method described above for converting to the glass composition expressed in cation %.

<Glass properties> (Glass transition temperature Tg) The optical glass can have a low glass transition temperature Tg by having the glass composition. For example, from the perspective of suppressing the degradation of the mold release film in precision press molding, suppressing the consumption of the press molding mold, etc., low Tg glass is preferred. The Tg of the optical glass is lower than 610°C, preferably in the order of 608°C or lower, 606°C or lower, 604°C or lower, 602°C or lower, 600°C or lower, 598°C or lower, 596°C or lower, 594°C or lower, 592°C or lower, and 590°C or lower. The lower limit of Tg is not particularly limited, for example, it can be 530°C or higher, preferably in the order of 540°C or higher, 550°C or higher, 555°C or higher, 560°C or higher, 565°C or higher, and 570°C or higher. The glass transition temperature Tg can be obtained by the method described below.

(Formula (1)) In the above optical glass, the refractive index nd and the glass transition temperature Tg satisfy the following formula (1). Formula (1): Tg＜2500*nd-4050 By satisfying formula (1), the above optical glass can take into account both high refractive index characteristics and press moldability. Generally speaking, there is a tendency that the higher the refractive index, the higher the Tg. In contrast, formula (1) indicates that although the refractive index is high, the Tg is low. The above optical glass preferably satisfies the following formula (1-1), more preferably satisfies the following formula (1-2), further preferably satisfies the following formula (1-3), further preferably satisfies the following formula (1-4), and further preferably satisfies the following formula (1-5). Formula (1-1): Tg＜2500*nd-4060 Formula (1-2): Tg＜2500*nd-4070 Formula (1-3): Tg＜2500*nd-4080 Formula (1-4): Tg＜2500*nd-4090 Formula (1-5): Tg＜2500*nd-4100

(Formula (2)) In the above optical glass, the refractive index nd and the Abbe number νd satisfy the following formula (2). Formula (2): νd＞-88.355*nd+201 The optical glass satisfying the above formula (2) shows low dispersion at a given refractive index and is useful as a material for optical elements.

(Refractive index nd) As long as the above formula (1) and the above formula (2) are satisfied, the refractive index nd of the above optical glass is not particularly limited. High refractive index glass is useful as a material for optical elements, and therefore, the refractive index nd of the above optical glass is preferably 1.8600 or more, and more preferably in the order of 1.8620 or more, 1.8640 or more, 1.8660 or more, 1.8680 or more, 1.8700 or more, 1.8720 or more, 1.8740 or more, and 1.8760 or more. As for the upper limit, it is preferably 1.9000 or less, and more preferably in the order of 1.8980 or less, 1.8960 or less, 1.8940 or less, 1.8920 or less, 1.8900 or less, 1.8880 or less, and 1.8860 or less.

(Abbe number νd) As long as the above formula (2) is satisfied, the Abbe number νd of the above optical glass is not particularly limited. Glass showing low dispersion is useful as a material for optical elements, and therefore, the Abbe number νd of the above optical glass is preferably 34.0 or more, and is further preferably in the order of 34.20 or more, 34.40 or more, 34.60 or more, 34.80 or more, 35.00 or more, 35.10 or more, 35.20 or more, 35.30 or more, 35.40 or more, 35.50 or more, 35.60 or more, 35.70 or more, 35.80 or more, 35.90 or more, 36.00 or more, 36.10 or more, and 36.20 or more. The upper limit is preferably 40.0 or less, and preferably 39.50 or less, 39.00 or less, 38.80 or less, 38.60 or less, 38.40 or less, 38.20 or less, 38.00 or less, 37.90 or less, 37.80 or less, and 37.76 or less. Considering that glass is used as a material for optical elements, increasing the refractive index of glass is equivalent to expanding the degree of freedom possessed by glass. From the perspective of expanding the above degree of freedom, it is better to increase the refractive index. On the other hand, if the dispersion is maintained and the refractive index is increased, the stability of the glass tends to decrease. From these perspectives, the Abbe number νd is preferably within the above range.

(Liquid phase temperature LT) As described above, the optical glass does not contain Ti or contains a small amount of Ti. The optical glass that does not contain Ti or contains a small amount of Ti and has a glass composition that realizes the desired Tg and optical constants described above has a liquid phase temperature LT of 1090°C or above. The liquid phase temperature LT may also be above 1100°C, above 1110°C, or above 1120°C. Regarding the upper limit, from the perspective of maintaining the viscosity during molding, it is preferably below 1230°C, and is further preferably below 1220°C, below 1210°C, below 1200°C, below 1190°C, and below 1180°C in this order.

In the present invention and this specification, the liquidus temperature LT is obtained by the following method. 5~8cc of glass is placed in a platinum crucible, heated in a furnace with an atmosphere temperature T for 2 hours, and after being in a molten state, taken out of the furnace, placed at room temperature, and cooled to room temperature. The room temperature is set to a temperature in the range of 20℃~30℃. The presence or absence of crystal precipitation in the cooled glass is determined by observation under an optical microscope (magnification 100 times). For different T (10℃ intervals), the presence or absence of crystal precipitation is determined by the above method. The lowest temperature T at which no crystal precipitation is observed is taken as the liquidus temperature.

(Specific gravity) From the perspective of reducing the weight of optical elements, it is better for optical glass to have a low specific gravity. The specific gravity of the optical glass is preferably 5.75 g/cc or less, and is more preferably 5.70 g/cc or less, 5.65 g/cc or less, and 5.58 g/cc or less in this order. In addition, the specific gravity of the optical glass can be 5.10 g/cc or more, and the lower the specific gravity, the better, so the lower limit is not particularly limited. In the present invention and this specification, the specific gravity is set to the value measured by the Archimedean method.

(Coloring λ ₅ , λ ₇₀ , λ ₈₀ ) The light transmittance of the glass, specifically, whether the light absorption end on the short wavelength side is suppressed from being longer wavelength, can be evaluated based on one or more of the coloring λ ₅ , λ ₇₀ and λ _80. Coloring λ ₅ refers to the wavelength at which the spectral transmittance (including surface reflection loss) of a glass with a thickness of 10 mm from the ultraviolet region to the visible region reaches 5%. λ ₇₀ indicates the wavelength at which the spectral transmittance measured by the method described for λ ₅ reaches 70%. λ ₈₀ indicates the wavelength at which the spectral transmittance measured by the method described for λ ₅ reaches 80%. λ ₅ , λ ₇₀ and λ ₈₀ shown in the table below are values measured in the wavelength range of 250~700nm. The spectral transmittance T(%) of the glass in the present invention and the specification can be expressed as follows: for a glass sample having two parallel planes after optical polishing, the intensity of light perpendicularly incident on one of the planes is set as I _in and the intensity of light emitted from the other plane after passing through the glass sample is set as I _out , and it is expressed as T(%) = I _out / I _in × 100. The absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated based on the chromaticity λ ₅ , λ ₇₀ and λ _80. When lenses are bonded to each other by a UV curing adhesive in order to produce a bonded lens, the following operation can be performed: UV rays are irradiated to the adhesive through an optical element to cure the adhesive. From the perspective of efficiently curing the UV-curing adhesive, the absorption end on the short-wavelength side of the spectral transmittance is preferably in a short wavelength range. As an indicator for quantitatively evaluating the absorption end on the short-wavelength side, one or more of the coloring indexes λ ₅ , λ ₇₀ , and λ ₈₀ can be used. The above optical glass can preferably show a λ ₅ below 380nm. λ ₅ is further preferably in the order of below 370nm, below 360nm, and below 350nm. The shorter the wavelength of λ ₅ , the better, and the lower limit is not particularly limited. The above optical glass can preferably show a λ ₇₀ below 430nm. λ ₇₀ is further preferably in the order of below 420nm, below 410nm, below 400nm, and below 395nm. The shorter the wavelength of λ ₇₀ , the better. The lower limit is not particularly limited. The optical glass can preferably show a λ ₈₀ of 510nm or less. λ ₈₀ is further preferably below 500nm, below 490nm, below 480nm, and below 470nm in the order of 500nm or less, 490nm or less, 480nm or less, and 470nm or less. The shorter the wavelength of λ ₈₀ , the better. The lower limit is not particularly limited.

<Glass manufacturing method> The optical glass can be obtained as follows: oxides, carbonates, sulfates, nitrates, hydroxides, etc. as raw materials are weighed and blended in a manner to obtain the target glass composition, and they are fully mixed to prepare a mixed batch, which is heated and melted in a melting container, and defoamed and stirred to prepare a homogeneous and bubble-free molten glass, which is molded to obtain an optical glass. Specifically, it can be produced using a known melting method.

[Glass raw material for press molding, its manufacturing method, and manufacturing method of glass molded body] According to the implementation mode of the present invention, a glass raw material for press molding made of the above optical glass, a glass molded body made of the above optical glass, and their manufacturing methods can be provided. The glass raw material for press molding refers to a glass block to be heated and provided for press molding. As an example of the glass raw material for press molding, there can be cited a glass block having a mass equivalent to that of a press-molded product, such as a glass raw material (glass gob for press molding) used for press molding of a precision press molding preform or an optical element blank. The glass raw material for press molding can be manufactured by a step of processing a glass molded body. The glass molded body can be manufactured by heating and melting the glass raw material as described above, and molding the obtained molten glass. Examples of processing methods for glass molded bodies include cutting, grinding, polishing, etc.

[Optical element blank and its manufacturing method] According to one embodiment of the present invention, an optical element blank made of the above optical glass can be provided. The optical element blank is a glass molded body having a shape similar to the shape of the optical element to be manufactured. The optical element blank can be manufactured by a method of molding glass into a shape after adding a processing surplus that will be removed by processing to the shape of the optical element to be manufactured. For example, the optical element blank can be manufactured by a method of heating and softening the glass raw material for press molding to perform press molding (reheat pressing method); a method of supplying a molten glass block to a press molding mold by a known method to perform press molding (direct pressing method), etc.

[Optical element and its manufacturing method] According to one embodiment of the present invention, an optical element made of 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.

As one method of manufacturing an optical element, there is a method of manufacturing an optical element by heating a preform for precision press molding and then performing precision press molding. Precision press molding can use a known press molding mold and apply a known molding method. The method of manufacturing an optical element by precision press molding is suitable for manufacturing aspherical lenses, micro lenses, diffraction gratings, etc.

In order to prevent the glass from fusing with the molding surface of the press-molding mold during precision press-molding and to improve the glass extension along the molding surface, it is preferred to coat the surface of the precision press-molding preform with a release film. Such a release film is known. The above-mentioned optical glass is a low-Tg glass having a glass transition temperature in the range described above, and it does not contain Ti or contains a small amount of Ti. The precision press-molding preform made of such glass is preferred from the viewpoint of suppressing the degradation of the release film. As an example of a release film, a carbon-containing film can be cited. The carbon-containing film can be, for example, a film having carbon as the main component (when the element content in the film is expressed in atomic %, the carbon content is greater than the content of other elements). As a method for forming the carbon-containing film, known methods such as vacuum evaporation, sputtering, and ion plating using a carbon raw material, and known methods such as thermal decomposition using a material gas such as hydrocarbon can be used.

FIG1 is a schematic cross-sectional view of a precision press molding apparatus. Precision press molding can be performed, for example, as described below. A preform for precision press molding (hereinafter, simply referred to as "preform") 4 is placed between a lower mold 2 and an upper mold 1 constituting a press molding mold, and then a nitrogen atmosphere is formed in the quartz tube 11, and a heater (not shown) is powered to heat the inside of the quartz tube 11. The temperature inside the press molding mold is set to a temperature at which the glass to be molded exhibits a viscosity of, for example, 10 ⁶ to 10 ¹⁰ dPa·s, and while maintaining this temperature, the push rod 13 is lowered to push the upper mold 1, thereby pressurizing the preform placed in the molding mold. After the pressurization, the pressurization pressure is released, and the glass molded product after the press molding is slowly cooled while maintaining contact with the lower mold 2 and the upper mold 1 to a temperature at which the viscosity of the glass reaches, for example, 10 ¹² dPa·s or more, and then quickly cooled to room temperature, and the glass molded product is taken out of the molding mold. In this way, an optical element can be obtained. It should be noted that in Figure 1, the holding member 10 holds the lower mold 2 and the shell mold 3, and the support rod 9 supports the upper mold 1, the lower mold 2, the shell mold 3, and the holding member 10, and is subjected to the pressure of the pressurization based on the push rod 13. A thermocouple 14 is inserted into the interior of the lower mold 2 to monitor the temperature inside the press molding mold.

As another method of manufacturing an optical element, a method of manufacturing an optical element by machining an optical element blank can be cited. Examples of machining include cutting, cutting, rough grinding, fine grinding, polishing, etc. Such a manufacturing method is suitable for manufacturing spherical lenses, prisms, etc. Implementation Example

The present invention is described in more detail below with reference to the embodiments. However, the present invention is not limited to the embodiments.

[Example No. 1 to No. 197] In order to achieve the glass composition shown in the table below, corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component, and the raw materials are weighed and fully mixed to prepare the blended raw materials. In the following table, "cat%" means "cation %", "wt%" means "mass %", "mol%" means "molar %", and the Sb ₂ O ₃ content is expressed as an added ratio. In addition, for example, "B ³⁺ /Si ⁴⁺ (cat%)" means the cation ratio of the B ³⁺ content to the Si ⁴⁺ content in the glass composition expressed in cation % and "B ₂ O ₃ /SiO ₂ (wt%)" means the mass ratio of the B ₂ O ₃ content to the SiO ₂ content in the glass composition expressed in mass %. The above aspects are also the same in the description of various cation ratios and various mass ratios in the following table. The prepared raw materials are placed in a platinum crucible, heated in a furnace set at 1250~1350℃, and melted for 120 minutes. The molten glass is stirred and homogenized, and then poured into a preheated mold, naturally cooled to near the glass transition temperature, and immediately placed in an annealing furnace. After being kept at a temperature around the glass transition temperature for about 30 minutes, it is slowly cooled at a slow cooling rate of -30℃/hour for 4 hours, and then naturally cooled in the furnace to room temperature, thereby obtaining the optical glasses of Examples No. 1 to No. 197 shown in the following table. Regarding the anion composition of each optical glass shown in the following table, the O ^2- content is 100 anion %.

<Physical property evaluation> The various physical properties of each optical glass shown in the following table were measured by the following method.

(1) Refractive index nd and Abbe number νd The refractive index nd and Abbe number νd of each optical glass were measured by the refractive index measurement method of the Japan Optical Glass Industry Association standard. For each optical glass, the calculated value on the right side of formula (1) and the calculated value on the right side of formula (2) are shown in the following table. If each formula is satisfied, it is indicated as "○" in the "Judgment" column.

(2) Glass transition temperature Tg Glass was fully ground in a mortar or the like as a sample, and a platinum cell was used as a sample container. The glass transition temperature Tg was measured by a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN Co., Ltd. at a heating rate of 10°C/min.

(3) Specific gravity The specific gravity was measured by the Archimedean method.

(4) Liquidus temperature LT The liquidus temperature LT was measured by the method described above.

(5) Coloring λ ₅ , λ ₇₀ , λ ₈₀ Using a glass sample with a thickness of 10±0.1 mm and two optically polished surfaces facing each other, the spectral transmittance T (%) was measured using a spectrophotometer. The wavelength (nm) at which T reached 5% was set as λ ₅ , the wavelength (nm) at which T reached 70% was set as λ ₇₀ , and the wavelength (nm) at which T reached 80% was set as λ ₈₀ .

The above results are shown in the following table.

[Preparation of a preform for precision pressing] For each of the above-mentioned embodiments, corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component in order to achieve the glass composition shown in the above table, and the raw materials are weighed and fully mixed to prepare the blended raw materials. As Comparative Example 1, in order to achieve the glass composition of Example 10 shown in Table 1 of Patent Document 1 (Japanese Patent Publication No. 2008-201661), corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component, and the raw materials are weighed and fully mixed to prepare the blended raw materials. As Comparative Example 2, in the manner of the glass composition of Example 34 shown in Table 1 of Patent Document 1 (Japanese Patent Publication No. 2008-201661), corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. are used as raw materials for introducing each component, the raw materials are weighed, and fully mixed to prepare the blended raw materials. A preparation example (Preparation Example 1) of a preform is described. The blended raw materials are placed in a platinum crucible, heated, and melted. The clarified and homogenized molten glass is made to flow out at a certain flow rate from a platinum alloy pipe whose temperature is adjusted to a temperature range that allows stable flow without glass devitrification, and is separated into molten glass blocks of the mass of the target preform by dripping or descending cutting. The separated molten glass block is received by a mold having a gas ejection port at the bottom, and a preform for precision pressing is formed while gas is ejected from the gas ejection port to float the glass block. By adjusting and setting the separation interval of the molten glass block, a flat spherical preform is obtained. As another example of making a preform (Preparation Example 2), there is a method as follows: after a homogeneous molten glass obtained by melting the prepared raw materials is cast into a casting mold and formed, the strain of the obtained molded body is removed by annealing, and it is cut or cut into a given size and shape to produce a plurality of glass sheets, the glass sheets are polished to make the surface smooth, and a preform made of glass of a given mass is produced. For the above-mentioned embodiment and the above-mentioned comparative example, a preform for precision press molding was produced by Production Example 2.

[Experiment to evaluate the degradation of release film] For each of the above-mentioned embodiments and the above-mentioned comparative examples, a carbon-containing film was coated on the surface of the manufactured preform, and the preform was heated in a nitrogen atmosphere. Specifically, after the furnace was evacuated, nitrogen was introduced in a manner to reach about 0.2 MPa, and the glass was heated for 360 seconds at a temperature at which the viscosity reached about 2.5 ¹⁰ poise. The temperature was increased from room temperature at 25°C/min, and the temperature was decreased at 20°C/min. After the above-mentioned heating, the surface of the preform was measured by SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Spectrometry) at an accelerating voltage of 3~25kV to confirm the presence of carbon, thereby evaluating whether there was any residual carbon-containing film on the surface of each preform. As a result of the above experiment, in the above embodiments, it was confirmed that a carbon-containing film remained on the surface of the preform. In contrast, in Comparative Examples 1 and 2, no carbon-containing film was confirmed to remain on the surface of the preform. The glass constituting the preform of Comparative Example 1 is a glass having a _TiO2 content of 0.83% by mass in the glass composition expressed in mass% (see Table 1 of Patent Document 1 (Japanese Patent Publication No. 2008-201661)). The glass transition temperature of the glass constituting the preform of Comparative Example 2 is 610°C (see Table 1 of Patent Document 1 (Japanese Patent Publication No. 2008-201661)). From the above results, it can be confirmed that, according to the glass having a _TiO2 content of 0.6 mass% or less and a glass transition temperature of less than 610°C as in the above-mentioned embodiment, it is possible to prevent the degradation of the release film.

In order to confirm the correlation between the above experiment and the suitability for precision pressing, the surface of the preform produced in the above embodiment and the above comparative example was coated with a carbon-containing film, introduced into a SiC press mold including upper and lower molds and a shell mold with a carbon-containing mold release film on the molding surface, and the molding mold and the preform were heated together in a nitrogen atmosphere to soften the preform, and precision pressing was performed to produce an aspherical biconvex lens with a diameter of 30 mm and a thickness of 4 mm in the optical axis direction. When precision pressing was performed in the above embodiment, no degradation of the mold release film was confirmed even after more than 150 shots, and mass production was good. In contrast, when the precision pressing of 100 shots was performed in the above comparative example, the release film deteriorated significantly, resulting in damage to the molding die, poor lens shape/appearance, etc., resulting in poor mass production. Based on the above results, it was confirmed that excellent mass production can be achieved in precision pressing by the glass of the above embodiment. In addition, according to the glass of the above embodiment, large-diameter lenses exceeding φ30mm, lenses with a wall thickness exceeding 4mm in the optical axis direction (preferably a lens with a maximum wall thickness exceeding 5mm), lenses with complex shapes, etc. can also be produced with high mass production.

Finally, the above implementations are summarized.

[1] An optical glass, wherein, in a glass composition expressed in mass %, a Li ₂ O content exceeds 0 mass %, a B ₂ O ₃ content is 3.00 mass % or more and 30.00 mass % or less, a SiO ₂ content exceeds 0 mass % and is 8.00 mass % or less, a La ₂ O ₃ content is 15.00 mass % or more and 55.00 mass % or less, a ZnO content is 3.00 mass % or more and 30.00 mass % or less, a TiO ₂ content is 0.60 mass % or less, a total content of Li ₂ O and ZnO (Li ₂ O+ZnO) is 10.20 mass % or more, a mass ratio of the B ₂ O ₃ content to the Li ₂ O content (B ₂ O ₃ /Li ₂ O) is 5.00 or more and 21.00 or less, a mass ratio of the SiO ₂ content to the Li ₂ O content (SiO ₂ /Li ₂ O) is less than 10.00, the glass transition temperature Tg of the optical glass is lower than 610°C, the liquidus temperature LT is greater than 1090°C, the refractive index nd and the glass transition temperature Tg satisfy the following formula (1), and the refractive index nd and the Abbe number νd satisfy the following formula (2), Formula (1): Tg＜2500*nd-4050 Formula (2): νd＞-88.355*nd+201. [2] The optical glass as described in [1], wherein, in the glass composition expressed as cation %, the cation ratio of the B ³⁺ content to the Si ⁴⁺ content (B ³⁺ /Si ⁴⁺ ) is greater than 1.25 and less than 11.00. [3] The optical glass as described in [1] or [2], wherein, in the glass composition expressed in mass _% , the mass ratio of the total content of _Nb2O5 , _TiO2 and _WO3 to the total content of _{SiO2 and B2O3 ( Nb2O5} + _TiO2 + _WO3 )/( _SiO2 + _B2O3 ) is 0.40 or more and 1.60 or less. [4] The optical glass as described in any one of [1] to [3], wherein, in the glass composition expressed in mass %, the mass ratio of the content of ZnO to the content of _WO3 (ZnO/ _{WO3 )} is 0.10 or more and 5.00 or less. [5] The optical glass as described in any one of [1] to [4], wherein, in the glass composition expressed in mass %, the mass ratio of Lu ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ (Lu ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Lu ₂ O ₃ )) is 0.50 or less. [6] The optical glass as described in any one of [1] to [5], wherein, in the glass composition expressed in cation %, the Li ⁺ content is 0.50 cation % or more. [7] The optical glass as described in any one of [1] to [6], wherein the refractive index nd is 1.8600 or more. [8] The optical glass as described in any one of [1] to [7], wherein the Abbe number νd is greater than or equal to 34.0 and less than or equal to 40.0. [9] The optical glass described in any one of [ ₁ ] to [8], wherein, in the glass composition expressed in mass %, the mass ratio of the total content of _Nb2O5 , _TiO2 and _WO3 to the total content of _SiO2 and _B2O3 ( _Nb2O5 + _TiO2 + _WO3 )/( _SiO2 + _B2O3 ) is 0.40 or more and _1.60 or _less , the _mass ratio of the ZnO content to the _WO3 content ( _ZnO / _WO3 ) is _0.10 or more and 5.00 or less, and the mass ratio of _{the Lu2O3} content to the total content of _La2O3 , _Gd2O3 , _Y2O3 and _Lu2O3 ( _{Lu2O3 /} (La2O3+Gd2O3+ _{Y2O3 + Lu2O3 ) is 0.10} or more and _{5.00 or less .} )) is less than 0.50, in the glass composition expressed in cation %, the cation ratio of B ³⁺ content to Si ⁴⁺ content (B ³⁺ /Si ⁴⁺ ) is greater than 1.25 and less than 11.00, the Li ⁺ content is greater than 0.50 cation %, the refractive index nd of the optical glass is greater than 1.8600, and the Abbe number νd is greater than 34.0 and less than 40.0. [10] An optical element, which is made of the optical glass described in any one of [1] to [9].

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 scope of the patent application, not the above description, and is intended to include all variations within the meaning and scope equivalent to the claim. For example, for the glass composition exemplified above, by adjusting the composition described in the specification, an optical glass of one embodiment of the present invention can be obtained. In addition, of course, any combination of two or more of the items exemplified in the specification or described as a preferred scope can be used.

1: Upper mold 2: Lower mold 3: Shell mold 4: Preform 9: Support rod 10: Retaining member 11: Quartz tube 13: Push rod 14: Thermocouple

FIG. 1 is a schematic cross-sectional view of a precision die-casting device.

1: Upper mold

2: Lower mold

3: Shell mold

4: Prefabricated parts

9: Support rod

10: Retaining components

11: Quartz tube

13: Putting

14: Thermocouple

Claims (10)

An optical glass, wherein, in a glass composition expressed in mass%, a Li ₂ O content exceeds 0 mass%, a B ₂ O ₃ content is 3.00 mass% or more and 30.00 mass% or less, a SiO ₂ content exceeds 0 mass% and is 8.00 mass% or less, a La ₂ O ₃ content is 15.00 mass% or more and 55.00 mass% or less, a ZnO content is 3.00 mass% or more and 30.00 mass% or less, a TiO ₂ content is 0.60 mass% or less, a total content of Li ₂ O and ZnO (Li ₂ O+ZnO) is 10.20 mass% or more, a mass ratio of the B ₂ O ₃ content to the Li ₂ O content (B ₂ O ₃ /Li 2 O) is 5.00 or more and 21.00 or less, a mass ratio of the SiO ₂ content to the Li ₂ O content (SiO ₂ /Li ₂ O) is 10.20 mass% or more, ₂ O) is less than 10.00, the glass transition temperature Tg of the optical glass is lower than 610°C, the liquidus temperature LT is above 1090°C, the refractive index nd and the glass transition temperature Tg satisfy the following formula (1), and the refractive index nd and the Abbe number νd satisfy the following formula (2), Formula (1): Tg＜2500*nd-4050 Formula (2): νd＞-88.355*nd+201. The optical glass as described in claim 1, wherein, in the glass composition expressed as cation %, a cation ratio of B ³⁺ content to Si ⁴⁺ content (B ³⁺ /Si ⁴⁺ ) is greater than or equal to 1.25 and less than or equal to 11.00. The optical glass according to claim 1, wherein, in the glass composition expressed in mass %, a mass ratio of the total content of _Nb2O5 , _TiO2 and _WO3 to the total content of _SiO2 and _{B2O3 (Nb2O5 + TiO2} + _WO3 )/( _SiO2 + _B2O3 ) is _0.40 or more and _1.60 or less _. The optical glass according to claim 1, wherein, in the glass composition expressed in mass %, a mass ratio of ZnO content to WO ₃ content (ZnO/WO ₃ ) is 0.10 or more and 5.00 or less. The optical glass according to claim 1, wherein, in the glass composition expressed in mass %, a mass ratio of Lu ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ (Lu ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Lu ₂ O ₃ )) is 0.50 or less. The optical glass as described in claim 1, wherein, in the glass composition expressed as cation %, the Li ⁺ content is 0.50 cation % or more. The optical glass according to claim 1, wherein the refractive index nd is greater than or equal to 1.8600. The optical glass according to claim 1, wherein the Abbe number νd is greater than or equal to 34.0 and less than or equal to 40.0. The optical glass according to claim 1, wherein, in the glass composition expressed in mass %, the mass ratio of the total content of Nb ₂ O ₅ , TiO ₂ and WO ₃ to the total content of SiO ₂ and B ₂ O ₃ (Nb ₂ O ₅ +TiO ₂ +WO ₃ )/(SiO ₂ +B ₂ O ₃ ) is 0.40 or more and 1.60 or less, the mass ratio of the ZnO content to the WO ₃ content (ZnO/WO ₃ ) is 0.10 or more and 5.00 or less, the mass ratio of the Lu ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Lu ₂ O ₃ (Lu ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Lu ₂ O ₃ )) is 0.50 or less, In the glass composition expressed by cation %, the cation ratio of B ³⁺ content to Si ⁴⁺ content (B ³⁺ /Si ⁴⁺ ) is greater than 1.25 and less than 11.00, the Li ⁺ content is greater than 0.50 cation %, the refractive index nd of the optical glass is greater than 1.8600, and the Abbe number νd is greater than 34.0 and less than 40.0. An optical element is made of the optical glass described in any one of claims 1 to 9.