JP2025003357A - Optical Glass and Optical Elements - Google Patents

Abstract

To provide an optical glass which has a small total content of Gd2O3 and Ta2O5 for the purpose of being reduced in cost, and has high reflectance.SOLUTION: In a glass composition by mol% on the basis of oxides. an SiO2 content is 1.00% or more and 30.00% or less, a B2O3 content is 1.00% or more and 40.00% or less, an La2O3 content is 5.00% or more and 40.00% or less, a Gd2O3 content is 0.00% or more and 3.50% or less, a Y2O3 content is 0.50% or more and 20.00% or less, a TiO2 content is 5.00% or more and 30.00% or less, a ZrO2 content is 0.00% or more and 20.00% or less, and an Nb2O5 content is 0.00% or more and 20.00% or less, and a composition ratio of the total content of a plurality of specific components is within a specified range, and a content molar ratio of two kinds of specific components is within the specified range.SELECTED DRAWING: None

Description

The present invention relates to optical glass and optical elements.

In recent years, optical glasses with high refractive indices have been proposed as materials for optical elements (see, for example, Patent Document 1).

WO2013/146378

Patent Document 1 (WO2013/146378) discloses a glass composition having a high total content of _{Gd2O3 and Ta2O5} as a glass composition that realizes a high refractive index (see the examples of _WO2013 / ₁₄₆₃₇₈ ). However, since _Gd2O3 and _Ta2O5 are expensive components whose unit prices have risen sharply in recent years, a glass having a low total content of _{Gd2O3 and Ta2O5} is _desirable in order to reduce the cost of glass _.

In view of the above, an object of one aspect of the present invention is to provide an optical glass having a high refractive index and a low total content of Gd ₂ O ₃ and Ta ₂ O ₅ .

One aspect of the present invention is as follows.
[1] In the glass composition based on oxides expressed in mol%,
_SiO2 content is 1.00% or more and 30.00% or less,
_B2O3 content is 1.00% or more and 40.00% or less _;
La2O3 content _is 5.00% or more and 40.00% or less,
_Gd2O3 content is 0.00% or more and 3.50% or less _{;
The Y2O3} content is 0.50% or more and 20.00% or less,
_TiO2 content is 5.00% or more and 30.00% or less,
_ZrO2 content is 0.00% or more and 20.00% or less;
The Nb ₂ O ₅ content is 0.00% or more and 20.00% or less,
The total content of Gd ₂ O ₃ and Ta ₂ O ₅ (Gd ₂ O ₃ + Ta ₂ O ₅ ) is 0.00% or more and 3.50% or less;
The total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is 26.50% or more;
The total content of TiO ₂ , ZrO ₂ and Nb ₂ O ₅ (TiO ₂ +ZrO ₂ +Nb ₂ O ₅ ) is 23.00% or more and 36.00% or less;
the total content of alkaline earth metal oxide RO and alkali metal oxide R ₂ O (RO + R ₂ O) is 3.50% or more;
the molar ratio of the Gd ₂ O ₃ content to the SiO ₂ content (Gd ₂ O ₃ /SiO ₂ ) is 0.00 or more and 0.23 or less;
the molar ratio of _{the B2O3} content to the _SiO2 content ( _B2O3 / _SiO2 ) is 0.80 or more and 1.56 or less _;
The molar ratio of the _SiO2 content to _{the La2O3} content ( _SiO2 / _La2O3 ) is 0.87 or less;
a molar ratio of the _Y2O3 content to _{the B2O3 content} ( _Y2O3 / _B2O3 ) of 0.15 or more _and 0.34 or less _, and _a molar ratio of the _TiO2 content to the _B2O3 content ( _TiO2 / _{B2O3 )} of 0.70 or more and 1.10 or less _;
Optical glass.
[2] The optical glass according to [1], having an Al ₂ O ₃ content of 0.00% or more and 2.00% or less.
[3] The optical glass according to [1] or [2], having an Nb ₂ O ₅ content of 0.10% or more and 20.00% or less.
[4] The optical glass according to any one of [1] to [3], having a _WO3 content of 0.00% or more and 0.40% or less.
[5] The optical glass according to any one of [1] to [4], in which the combined content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ ) is 26.50% or more and 35.00% or less.
[6] The optical glass according to any one of [1] to [5], in which the combined content of alkaline earth metal oxide RO and alkali metal oxide R ₂ O (RO+R ₂ O) is 3.50% or more and 10.50% or less.
[7] The optical glass according to any one of [1] to [6], in which the molar ratio of the Y ₂ O ₃ content to the B ₂ O ₃ content (Y ₂ O ₃ /B ₂ O ₃ ) is 0.17 or more and 0.34 or less.
[8] The optical glass according to any one of [1] to [7], in which the molar ratio of the B ₂ O ₃ content to the SiO ₂ content (B ₂ O ₃ /SiO ₂ ) is 1.20 or more and 1.56 or less.
[9] The optical glass according to any one of [1] to [8], in which the molar ratio of the SiO ₂ content to the La ₂ O ₃ content (SiO ₂ /La ₂ O ₃ ) is 0.50 or more and 0.87 or less.
[10] The optical glass according to any one of [1] to [9], in which the combined content of Gd ₂ O ₃ and Ta ₂ O ₅ (Gd ₂ O ₃ +Ta ₂ O ₅ ) is from 0.00% to 2.50%.
[11] The Al ₂ O ₃ content is 0.00% or more and 2.00% or less;
_{The Nb2O5} content is 0.10% or more and 20.00% or less,
The _WO3 content is 0.00% or more and 0.40% or less,
The total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is 26.50% or more and 35.00% or less,
the total content (RO+ _R2O ) of alkaline earth metal oxide RO and alkali metal oxide _R2O is 3.50% or more and 10.50% or less;
The molar ratio of the _Y2O3 content to _{the B2O3 content} ( _{Y2O3 /B2O3 )} is 0.17 _or more and 0.34 or less _,
The molar ratio of _{the B2O3} content to the _SiO2 content ( _B2O3 / _SiO2 ) is 1.20 or more and 1.56 or less _;
The optical glass according to any one of [ _{1 ]} to _{[10] ,} in which the molar ratio of the SiO2 content to the _La2O3 content ( _SiO2 / _La2O3 ) is 0.50 or more and 0.87 or _less , and the total content of _Gd2O3 and _{Ta2O5 ( Gd2O3} + _{Ta2O5 )} is 0.00% or more and 2.50% or less.
[12] An optical element comprising the optical glass according to any one of [1] to [11].

According to one aspect of the present invention, it is possible to provide an optical glass having a high refractive index that has a small total content of Gd ₂ O ₃ and Ta ₂ O ₅ , and an optical element made of this optical glass.

[Optical glass]
In the present invention and this specification, the glass composition of optical glass is expressed as a glass composition based on oxides expressed in mol%. Here, "glass composition based on oxides" refers to a glass composition obtained by converting the glass raw materials into oxides that exist in the glass after being completely decomposed during melting. In the glass composition expressed in mol%, the glass composition is expressed on a molar basis (mol%, molar ratio). Hereinafter, for glass compositions expressed in mol%, "mol%" will also be simply referred to as "%".

In the present invention and this specification, the content of a component being 0%, 0.0% or 0.00%, or not containing or not introducing, means that the component is substantially not contained, and indicates that the content of the component is at or below the impurity level. At or below the impurity level means, for example, less than 0.01%. "0%" can mean, for example, "0.0%" or "0.00%". The content of a certain component being "0% or more", "0.0% or more", or "0.00% or more" means that the component is an optional component.

The glass composition of the present invention and this specification can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). For example, quantitative analysis is performed for each element using ICP-AES. The analytical values are then converted to oxide notation. The analytical values obtained by ICP-AES may contain a measurement error of, for example, about ±5% of the analytical value. Therefore, the oxide notation values converted from the analytical values may also contain an error of about ±5%.

In this invention and this specification, the refractive index refers to the refractive index nd at the helium d line (wavelength 587.56 nm).

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

The above optical glass (sometimes simply referred to as "glass") will be described in more detail below.

<Glass composition>
_SiO2 is a glass network component, and as its content increases, the viscosity of the glass increases, but the melting property tends to decrease. From the above viewpoints, the _SiO2 content is 1.00% or more and 30.00% or less.
The _SiO2 content is preferably 2.00% or more, more preferably 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 13.50% or more, 14.00% or more, and 14.50% or more in that order.
Further, the _SiO2 content is preferably 29.00% or less, more 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, 17.50% or less, 17.00% or less, and 16.50% or less.

B ₂ O ₃ is a glass network component and contributes to improving meltability. From the above viewpoint, the B ₂ O ₃ content is 1.00% or more, preferably 2.00% or more, more preferably 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 14.00% or more, 15.00% or more, 16.00% or more, 17.00% or more, 17.50% or more, 18.00% or more, 18.50% or more, 19.00% or more, and 19.50% or more in this order.
On the other hand, the effect of volatilization increases with the content of _{B 2} O _3. Therefore, from the viewpoint of ease of optical property control, the B _{2 O 3} content is 40.00% or less, preferably 39.00% or less, more preferably 38.00% or less, 37.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 33.00% or less, 32.00% or less, 31.00% or less, 30.00% or less, 29.00% or less, 28.00% or less, 27.00% or less, 26.00% or less, 25.00% or less, 24.00% or less, 23.50% or less, 23.00% or less, and 22.50% or less in that order.

Regarding the molar ratio ( _B2O3 / _{SiO2 )} of _{the B2O3} content to the _SiO2 content, when the value of this molar ratio is small, the glass tends to become highly dispersed, and when the value of this molar ratio is large, the refractive index of the glass tends to decrease. From the above viewpoints, _the molar ratio ( _B2O3 / _SiO2 ) is 0.80 or more and 1.56 or less.
The molar ratio (B ₂ O ₃ /SiO ₂ ) is preferably 0.85 or more, and more preferably 0.90 or more, 0.95 or more, 1.00 or more, 1.05 or more, 1.10 or more, 1.15 or more, 1.20 or more, 1.21 or more, 1.22 or more, and 1.23 or more in that order.
Further, the molar ratio (B ₂ O ₃ /SiO ₂ ) is preferably 1.55 or less, and more preferably 1.54 or less, 1.53 or less, 1.52 or less, 1.51 or less, 1.50 or less, 1.49 or less, and 1.48 or less in that order.

The total content of _{Gd2O3 and Ta2O5 (Gd2O3 + Ta2O5) is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. Gd2O3 and Ta2O5 are components that increase the refractive index of} glass _, but from the viewpoint of reducing the _cost of _glass , the smaller the total content of _Gd2O3 and _Ta2O5 ( _{Gd2O3 + Ta2O5 )} the more preferable. The total content of Gd ₂ O ₃ and Ta ₂ O ₅ (Gd ₂ O ₃ + Ta ₂ O ₅ ) in the above glass is 3.50% or less, preferably 3.00% or less, more preferably 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less, in that order, and most preferably 0.00%.
The contents of Gd ₂ O ₃ and Ta ₂ O ₅ will be described later.

_La2O3 is _a component that contributes to increasing the refractive _index and decreasing the dispersion of glass. When the _La2O3 content is low, the refractive index tends to decrease, and when the _La2O3 content is high, the glass tends to crystallize easily. From the above viewpoints, _{the La2O3 content} is 5.00% or more and 40.00 _% or less.
The _La2O3 content is preferably 6.00% or more, and more preferably in the order of 7.00 _% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 14.00% or more, 15.00% or more, 16.00% or more, 17.00% or more, 18.00% or more, 19.00% or more, 20.00% or more, 20.50% or more, 21.00% or more, 21.50% or more, 22.00% or more, and 22.50% or more.
Further, _{the La2O3} content is preferably 39.00% or less, and more preferably 38.00% or less, 37.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 33.00% or less, 32.00% or less, 31.00% or less, 30.00% or less, 29.00% or less, 28.00% or less, 27.50% or less, 27.00% or less, 26.50% or less, 26.00% or less, 25.50% or less, 25.00% or less, 24.50% or less, 24.00% or less, and 23.50% or less in that order.

The Gd ₂ O ₃ content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. Gd ₂ O ₃ is a component that contributes to the high refractive index and low dispersion of glass. However, Gd ₂ O ₃ is a component with a high unit price, increases the specific gravity, makes the glass easier to crystallize, and is also a component that reduces the melting property of the glass. Therefore, when Gd ₂ O ₃ is contained in glass, it is preferable to contain it in as small an amount as possible. From the above viewpoint, the Gd ₂ O ₃ content is 3.50% or less, and is preferably 3.00% or less, 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, 0.50% or less in that order, and is most preferably 0.00%.

_Y2O3 is a component that contributes to increasing the refractive index and decreasing the dispersion of the glass. However, if _{the Y2O3} content is high _, the glass tends to crystallize easily. From the above viewpoints, _{the Y2O3} content is 0.50% or more and 20.00% or less.
_{The Y2O3} content is preferably 1.00% or more, and more preferably 2.00% or more, 3.00% or more, 3.50% or more, 4.00% or more, 4.50% or more, and 5.00% or more in that order.
Further, _{the Y2O3} content is preferably 19.00% or less, and more preferably 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.00% or less, 6.50% or less, 6.00% or less, and 5.50% or less.

_From the viewpoint of increasing the refractive index of _{the glass, the total content of La2O3, Gd2O3 and Y2O3 ( La2O3 + Gd2O3 + Y2O3 )} is 26.50% or more, preferably 27.00% or more, and more preferably 27.50% or more, _27.60 % or more, 27.70% or more, 27.80% or more, 27.90% _or more, and 28.00% or more in that order.
From the viewpoint of suppressing crystallization of the glass, the total content (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is preferably 40.00% or less, and more preferably 35.00% or less, 34.00% or less, 33.00% or less, 32.50% or less, 32.00% or less, 31.50% or less, 31.00% or less, 30.50% or less, 30.00% or less, 29.50% or less, and 29.00% or less, in that order.

The molar ratio of the Gd ₂ O ₃ content to the SiO ₂ content (Gd ₂ O ₃ /SiO ₂ ) is equal to or greater than 0.00, and can be equal to or greater than 0.00, 0.00 or greater. From the viewpoint of reducing the specific gravity of the glass, the molar ratio ( _Gd2O3 / _SiO2 ) is 0.23 or less, preferably 0.22 or less, and more preferably _0.21 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, and 0.01 or less, and is most preferably 0.00.

From the viewpoint of increasing the refractive index of the glass, the molar ratio of the _SiO2 content to _{the La2O3} content ( _SiO2 / _La2O3 ) is 0.87 or less, preferably 0.85 or less, and more preferably _0.80 or less, 0.79 or less, 0.78 or less, 0.76 or less, 0.75 or less, 0.74 or less, 0.73 or less, 0.72 or less, and 0.71 or less, in that order.
The molar ratio (SiO ₂ /La ₂ O ₃ ) can be more than 0.00, and from the viewpoint of maintaining glass stability, is preferably 0.05 or more, and more preferably 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, and 0.60 or more, in that order.

Regarding the molar _ratio ( _Y2O3 / _{B2O3) of the Y2O3 content to the B2O3 content , as} the value of this molar ratio decreases, the refractive index of the glass tends to decrease, and as the value of this molar ratio increases _, the glass tends to crystallize easily. From the above viewpoints, _{the molar ratio (Y2O3/B2O3 ) is 0.15} or more and _0.34 or less.
The molar ratio (Y ₂ O ₃ /B ₂ O ₃ ) is preferably 0.16 or more, and more preferably 0.17 or more, 0.18 or more, 0.19 or more, 0.20 or more, 0.21 or more, 0.22 or more, and 0.23 or more in that order.
Further, the molar ratio (Y ₂ O ₃ /B ₂ O ₃ ) is preferably 0.33 or less, and more preferably 0.32 or less, 0.31 or less, 0.30 or less, 0.29 or less, and 0.28 or less in that order.

_TiO2 is a component that increases the refractive index of glass. However, _TiO2 is a component that decreases the transmittance of glass, and the glass tends to crystallize more easily when the TiO2 content is high. From the above viewpoints, the _TiO2 content is 5.00% or more and 30.00% or less.
The _TiO2 content is preferably 6.00% or more, and more preferably in the following order: 7.00% or more, 8.00% or more, 9.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 14.00% or more, 15.00% or more, 15.50% or more, 16.00% or more, 16.50% or more, and 17.00% or more.
Further, the _TiO2 content is preferably 29.00% or less, and more 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, 22.50% or less, 22.00% or less, 21.50% or less, 21.00% or less, and 20.50% or less.

The _ZrO2 content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. _ZrO2 is a component that contributes to increasing the refractive index and low dispersion of glass. However, _ZrO2 is a component that increases the viscosity of glass, and as its content increases, the glass tends to become more easily devitrified. From the above viewpoints, the _ZrO2 content is 20.00% or less, preferably 19.00% or less, and more preferably 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.50% or less, 9.00% or less, 8.50% or less, 8.00% or less, and 7.50% or less in that order.
In addition, the _ZrO2 content is preferably 1.00% or more, and more preferably 2.00% or more, 2.50% or more, 3.00% or more, 3.50% or more, 4.00% or more, 4.50% or more, 5.00% or more, 5.50% or more, 6.00% or more, and 6.50% or more in that order.

The Nb ₂ O ₅ content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. Nb ₂ O ₅ is a component that contributes to increasing the refractive index and decreasing the dispersion of the glass. From the viewpoint of controlling the dispersibility of the glass, the Nb ₂ O ₅ content is 20.00% or less, preferably 19.00% or less, and more preferably 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.50% or less, 6.00% or less, 5.50% or less, 5.00% or less, and 4.50% or less in that order.
The Nb ₂ O ₅ content is preferably 0.10% or more, more preferably 0.50% or more, 1.00% or more, and further preferably 1.50% or more in that order.

From the viewpoint of suppressing crystallization of glass and suppressing high dispersion, the total content of TiO ₂ , ZrO ₂ and Nb ₂ O ₅ (TiO ₂ + ZrO ₂ + Nb ₂ O ₅ ) is 36.00% or less, preferably 34.00% or less, and more preferably 33.50% or less, 33.00% or less, 32.50% or less, 32.00% or less, 31.50% or less, 31.00% or less, 30.50% or less, 30.00% or less, and 29.50% or less.
From the viewpoint of increasing the refractive index of the glass, the total content (TiO ₂ +ZrO ₂ +Nb ₂ O ₅ ) is 23.00% or more, preferably 24.00% or more, and more preferably 24.50% or more, 25.00% or more, 25.50% or more, 26.00% or more, 26.50% or more, 27.00% or more, 27.50% or more, 28.00% or more, and 28.50% or more in that order.

Regarding the molar ratio ( _TiO2 / _B2O3 ) of the _TiO2 content to _{the B2O3} content, when the value of this molar ratio is _large , the glass tends to become highly dispersed, and when the value of this molar ratio is small, the refractive index of the glass tends to decrease. From the above viewpoints, the molar ratio ( _TiO2 / _{B2O3 )} is 0.70 or more and 1.10 or less.
The molar ratio (TiO ₂ /B ₂ O ₃ ) is preferably 0.72 or more, more preferably 0.74 or more, 0.75 or more, and further preferably 0.76 or more in that order.
Further, the molar ratio (TiO ₂ /B ₂ O ₃ ) is preferably 1.09 or less, and more preferably 1.08 or less, 1.07 or less, 1.06 or less, 1.05 or less, 1.04 or less, and 1.03 or less in that order.

When alkaline earth metal oxide is represented as RO and alkali metal oxide is represented as R ₂ O, the total content of alkaline earth metal oxide RO and alkali metal oxide R ₂ O (RO + R ₂ O) is 3.50% or more, preferably 3.60% or more, from the viewpoint of reducing the viscosity of the glass, and more preferably 3.70% or more, 3.80% or more, 3.90% or more, 4.00% or more, 4.10% or more, 4.20% or more, 4.30% or more, 4.40% or more, 4.50% or more, 4.60% or more, 4.70% or more, 4.80% or more, 4.90% or more, 5.00% or more, 5.10% or more, 5.20% or more, 5.30% or more, 5.40% or more, 5.50% or more, 5.60% or more, and 5.70% or more in that order.
On the other hand, from the viewpoint of suppressing crystallization of the glass, the total content (RO+ _R2O ) is preferably 12.00% or less, and more preferably 11.50% or less, 11.00% or less, 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, 7.40% or less, 7.30% or less, 7.20% or less, and 7.10% or less, in that order.

Regarding the content of each component of the alkali metal oxide R ₂ O, the Li ₂ O content is 0.00% or more, and can be 0.00% or more. From the viewpoints of further improving the thermal stability of the glass, suppressing a decrease in the glass transition temperature (thereby improving machinability), and improving chemical durability and weather resistance, the Li ₂ O content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, and 2.00% or less in that order.
The content of each of Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O is 0.00% or more, and can be 0.00% or more than 0.00%. Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O all have the function of improving the melting property of glass, but when the content of these elements increases, the thermal stability, chemical durability, weather resistance and machinability of glass tend to decrease. Therefore, the content of each of Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O is preferably 5.00% or less, more preferably 4.00% or less, 3.00% or less, and 2.00% or less in that order.
Rb ₂ O and Cs ₂ O are expensive components, and are less suitable for general-purpose glass than Li ₂ O, Na ₂ O, and K ₂ O. From the viewpoints of improving the meltability of glass, lowering the glass transition temperature Tg, and lowering the specific gravity of glass while maintaining the thermal stability, chemical durability, weather resistance, and machinability of glass, it is preferable that the alkali metal oxide R ₂ O contained in the above glass is one or more selected from the group consisting of Li ₂ O, Na ₂ O, and K ₂ O.

The alkaline earth metal oxide RO contained in the glass is preferably one or more selected from the group consisting of MgO, CaO, SrO and BaO. The content of each of MgO, CaO, SrO and BaO is 0.00% or more, and can be 0.00% or more than 0.00%. From the viewpoint of suppressing devitrification of the glass and realizing the desired optical properties, the content of each of MgO, CaO, SrO and BaO is preferably 8.00% or less, more preferably 7.00% or less, and further preferably 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less in that order.

Ta ₂ O ₅ is an expensive component. From the viewpoint of reducing the cost of the glass, the Ta ₂ O ₅ content is preferably 2.50% or less, more preferably 2.00% or less, 1.50% or less, 1.00% or less, and 0.50% or less in that order, and is most preferably 0.00%.

The Al ₂ O ₃ content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. From the viewpoint of suppressing crystallization of glass, the Al ₂ O ₃ content is preferably 2.00% or less, more preferably 1.50% or less, 1.00% or less, and 0.50% or less in that order, and is most preferably 0.00%.

The _WO3 content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. _WO3 is a component that contributes to the high refractive index and low dispersion of glass, but when its content increases, the transmittance of glass tends to decrease. From the viewpoint of suppressing the decrease in the transmittance of glass, the _WO3 content is preferably 0.40% or less, more preferably 0.30% or less, 0.20% or less, and 0.10% or less in that order, and most preferably 0.00%.

_{The Bi2O3} content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. _Bi2O3 is _a component that contributes to the high refractive index and low dispersion of glass, but when its content increases, the transmittance of glass tends to decrease. From the viewpoint of suppressing the decrease in the transmittance of glass, _{the Bi2O3} content is preferably 0.40% or less, more preferably 0.30% or less, 0.20% or less, and 0.10 or less in that order, and most preferably 0.00%.

The ZnO content is 0.00% or more, and can be 0.00%, 0.00% or more, or more than 0.00%. ZnO is a component that lowers the melting temperature of glass and also a component that lowers the glass transition temperature Tg. The ZnO content is preferably 0.10% or more, more preferably 0.50% or more, 0.70% or more, 0.90% or more, and 1.00% or more in that order.
On the other hand, from the viewpoint of suppressing crystallization of the glass, the ZnO content is preferably 12.00% or less, and more preferably 11.00% or less, 10.00% or less, 9.00% or less, and 8.00% or less in that order.

Concerning other glass components, taking into consideration the environmental impact, the _As2O3 content is preferably 0.10% or less, more preferably 0.01% or less, and most preferably 0.00%. Also, taking into consideration the environmental impact, the _PbO content is preferably 1.00% or less, more preferably 0.50% or less, and more preferably 0.10% or less, and most preferably 0.00%.

Sb ₂ O ₃ is a component that can be added as a clarifier. Although a small amount of Sb ₂ O ₃ can suppress the decrease in light transmittance caused by the inclusion of impurities such as Fe, the coloring of the glass tends to increase when the amount of Sb 2 O 3 added is increased. Therefore, the amount of Sb ₂ O ₃ added is preferably 0.00% or more and 0.10% or less, more preferably 0.00% or more and 0.08% or less, and even more preferably 0.00% or more and 0.05% or less, by the external percentage. The Sb ₂ O ₃ content by the external percentage means the content of Sb ₂ O ₃ expressed by mass% when the total content of glass components other than Sb ₂ O ₃ is 100 mass%.

_SnO2 can also be added as a clarifier, but if it is added in an amount exceeding 1.00% by weight, the glass will be colored, and when the glass is heated and softened and reshaped by press molding, etc., Sn will become the starting point for crystal nucleation, causing a tendency for devitrification. Therefore, the amount of _SnO2 added is preferably 0.00% or more and 1.00% or less by weight, more preferably 0.00% or more and 0.50% or less, and particularly preferably not added. The _SnO2 content by weight refers to the content of _SnO2 expressed in mass% when the total content of glass components other than _SnO2 is taken as 100 mass%.

<Glass properties>
(Refractive index nd)
The glass can be a high refractive index glass by having the above glass composition. From the viewpoint of usefulness as a material for optical elements, the refractive index nd of the glass is preferably 1.9430 or more, more preferably 1.9450 or more, 1.9500 or more, and further preferably 1.9520 or more in that order.
From the viewpoint of usefulness as a material for optical elements, the refractive index nd of the above glass is preferably 1.9800 or less, and more preferably 1.9790 or less, 1.9780 or less, 1.9770 or less, 1.9760 or less, 1.9750 or less, 1.9740 or less, 1.9730 or less, 1.9720 or less, 1.9710 or less, 1.9700 or less, 1.9690 or less, 1.9680 or less, 1.9670 or less, 1.9660 or less, 1.9650 or less, 1.9640 or less, 1.9630 or less, 1.9620 or less, 1.9610 or less, 1.9600 or less, 1.9590 or less, 1.9580 or less, 1.9570 or less, 1.9560 or less, and 1.9550 or less in that order.

(Abbe number vd)
The above glass has the above glass composition and thus can exhibit low dispersion.
From the standpoint of usefulness as a material for optical elements, the Abbe number vd of the above glass is preferably 30.00 or greater, more preferably 30.20 or greater, 30.50 or greater, 31.00 or greater, 31.50 or greater, 32.00 or greater, or 32.10 or greater.
From the viewpoint of usefulness as a material for optical elements, the Abbe number vd of the above glass is preferably 34.00 or less, more preferably 33.50 or less, 33.00 or less, and further preferably 32.50 or less, in that order.

(specific gravity)
The refractive power of the optical elements that make up an optical system is determined by the refractive index of the glass that makes up the optical element and the curvature of the optical function surface of the optical element (the surface through which the light rays to be controlled enter and exit). If you try to increase the curvature of the optical function surface, the thickness of the optical element also increases. As a result, the optical element becomes heavier. In contrast, if glass with a high refractive index is used, it is possible to obtain a large refractive power without increasing the curvature of the optical function surface.
From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, it will be possible to reduce the weight of an optical element having a certain refractive power.
From the above viewpoints, the specific gravity of the glass is preferably 5.50 or less, and more preferably 5.20 or less, 5.19 or less, 5.18 or less, 5.17 or less, 5.16 or less, 5.15 or less, 5.10 or less, 5.05 or less, and 5.00 or less in that order.
Since a lower specific gravity is preferable from the viewpoint of reducing the weight of the optical element, the lower limit of the specific gravity of the glass is not particularly limited. In one embodiment, the specific gravity of the glass can be, for example, 4.80 or more, 4.85 or more, 4.90 or more, 4.92 or more, 4.93 or more, 4.94 or more, or 4.95 or more.
In the present invention and this specification, the "specific gravity" is a value measured by Archimedes' method.

(Coloring degree λ ₅ , λ ₇₀ )
The light transmittance of the glass, specifically, the suppression of the shift of the light absorption edge on the short wavelength side to the long wavelength side, can be evaluated by one or more of the coloring degrees _λ5 and _{λ70 .} λ ₇₀ represents _the wavelength at which the spectral transmittance (including surface reflection loss) of glass with a thickness of 10±0.1 mm is 5% from the ultraviolet region to the visible region. It represents the wavelength at which the measured spectral transmittance is 70%. The λ ₅ and λ ₇₀ shown in the table below are values measured in the wavelength range of 250 to 700 nm. The spectral transmittance T (%) of a glass sample having two optically polished parallel flat surfaces is expressed as the intensity of light incident perpendicularly on one of the flat surfaces, I _in , and the intensity of light transmitted through the glass sample. When the intensity of the light emitted from the other surface is _Iout ,
T (%)=I _out /I _in ×100
It is expressed as:
The coloring degree _λ5 and _λ70 allow quantitative evaluation of the absorption edge on the short wavelength side of the spectral transmittance. For example, when lenses are bonded together with an ultraviolet-curing adhesive to produce a cemented lens, In such cases, the adhesive is cured by irradiating it with ultraviolet light through an optical element. From the viewpoint of efficiently curing an ultraviolet-curable adhesive, it is preferable to use an absorption edge on the short wavelength side of the spectral transmittance. It is preferable that the absorption edge is in the short wavelength region. As an index for quantitatively evaluating the absorption edge on the short wavelength side, one or more of the coloring degrees _λ5 and _λ70 can be used.
The _λ5 of the above glass can preferably exhibit a _λ5 of 370 nm or less. _{The λ5} is more preferably 369 nm or less, and further preferably 368 nm or less. The shorter the wavelength, the more _{the λ5} . In one embodiment, λ ₅ can be 340 nm or more, 341 nm or more, 342 nm or more, 343 nm or more, 344 nm or more, 345 nm or more, 346 nm or more, or 347 nm or more.
The glass preferably exhibits a λ ₇₀ of 440 nm or less. The λ ₇₀ may be 439 nm or less, 438 nm or less, 437 nm or less, 436 nm or less, 435 nm or less, 434 nm or less, 433 nm or less, 432 nm or less, 431 nm or less, or 430 nm or less. , 429 nm or less, 428 nm or less, and 427 nm or less are more preferable in that order. The shorter the wavelength of λ ₇₀ , the more preferable it is, and the lower limit is not particularly limited. In one embodiment, λ ₇₀ is 390 nm or more, 391 nm or more, or 392 nm or more. , 393 nm or greater, or 394 nm or greater.

(Glass transition temperature Tg)
From the viewpoint of machinability (more specifically, from the viewpoint of resistance to breakage when mechanically processing the glass such as cutting, milling, grinding, polishing, etc.), the glass transition temperature Tg of the above-mentioned glass is preferably 680° C. or higher, and more preferably 685° C. or higher, 686° C. or higher, 687° C. or higher, 688° C. or higher, 690° C. or higher, 691° C. or higher, 692° C. or higher, 693° C. or higher, 694° C. or higher, 695° C. or higher, 696° C. or higher, 697° C. or higher, 698° C. or higher, 699° C. or higher, and 700° C. or higher in that order.
On the other hand, from the viewpoint of reducing the burden on the annealing furnace and the molding die, the glass transition temperature Tg of the above glass is preferably 750° C. or less, and more preferably 750° C. or less, 745° C. or less, 744° C. or less, 743° C. or less, 742° C. or less, 741° C. or less, 740° C. or less, 735° C. or less, 730° C. or less, and 725° C. or less in that order.
The glass transition temperature Tg is determined by a differential scanning calorimeter at a heating rate of 10° C./min.

<Method of manufacturing optical glass>
The optical glass can be obtained by weighing, preparing and thoroughly mixing raw materials such as oxides, carbonates, sulfates, nitrates and hydroxides so as to obtain the desired glass composition, heating and melting the mixture in a melting vessel, degassing and stirring the mixture to produce a homogeneous, bubble-free molten glass, and then molding the glass. Specifically, the glass can be produced by using a known melting method.

[Glass material for press molding, optical element blank, and manufacturing method thereof]
Another aspect of the present invention is
a glass material for press molding comprising the optical glass;
an optical element blank made of the optical glass;
Regarding.

According to another aspect of the present invention,
a method for producing a glass material for press molding, comprising a step of molding the optical glass into a glass material for press molding;
A method for producing an optical element blank, comprising a step of press-molding the glass material for optical glass press molding using a press mold to produce an optical element blank;
A method for producing an optical element blank, comprising the step of forming the optical glass into an optical element blank;
will also be provided.

An optical element blank is an optical element base material that approximates the shape of the desired optical element, with polishing allowances (surface layers to be removed by polishing) and, if necessary, grinding allowances (surface layers to be removed by grinding) added to the shape of the optical element. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) in which a molten glass obtained by melting an appropriate amount of the above glass is press-molded. In another embodiment, the optical element blank can also be produced by solidifying the molten glass obtained by melting an appropriate amount of the above glass.

In another embodiment, a glass material for press molding is prepared, and the prepared glass material for press molding is press molded to produce an optical element blank.

Press molding of glass material for press molding can be carried out by a known method in which the glass material for press molding in a heated and softened state is pressed in a press mold. Both heating and press molding can be carried out in air. By annealing after press molding to reduce distortion inside the glass, a homogeneous optical element blank can be obtained.

Glass materials for press molding include glass gobs for press molding that are used for press molding as is to produce optical element blanks, as well as glass gobs for press molding that are machined by cutting, grinding, polishing, etc. and then used for press molding. Cutting methods include a method in which a groove is formed in the area of the surface of the glass plate to be cut by a method called scribing, and local pressure is applied to the grooved area from the back side of the surface on which the groove is formed, thereby breaking the glass plate at the grooved area, and a method in which the glass plate is cut by a cutting blade. Grinding and polishing methods include barrel polishing, etc.

A glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and then cutting this glass plate into multiple glass pieces. Alternatively, an appropriate amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating and softening a glass gob for press molding and press molding it. The method of producing an optical element blank by reheating and softening glass and press molding it is called the reheat press method, as opposed to the direct press method.

[Optical element and method of manufacturing the same]
Another aspect of the present invention is
The present invention relates to an optical element made of the optical glass.

The optical element is manufactured using the optical glass. In the optical element, the glass surface may be coated with one or more layers of coating, such as a multilayer film such as an anti-reflection film.

According to another aspect of the present invention,
A method for producing an optical element, comprising the step of producing an optical element by grinding and/or polishing the optical element blank described above;
will also be provided.

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

The optical element made of the optical glass is also suitable as a lens constituting a cemented optical element. Examples of cemented optical elements include a cemented lens in which lenses are cemented together, and a lens and a prism are cemented together. For example, a cemented optical element can be produced by precisely machining (for example, spherical polishing) the cemented surfaces of two optical elements to be cemented so that the shape is an inverted shape, applying an ultraviolet-curing adhesive used for bonding cemented lenses, bonding them together, and then irradiating ultraviolet rays through the lens to cure the adhesive. In this way, the optical glass is preferable for producing a cemented optical element. By producing a plurality of optical elements to be cemented using a plurality of types of glass with different Abbe numbers νd and cementing them together, an element suitable for correcting chromatic aberration can be produced.

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

[Example 1]
<No. 001-118>
In order to obtain the glass composition (unit: mol %) shown in the table below, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component, and the raw materials were weighed and thoroughly mixed to obtain blended raw materials.
The mixed raw materials were placed in a platinum crucible and heated in a furnace set at 1350° C. for 2 hours. The molten glass was stirred to homogenize it, and then poured into a preheated mold and allowed to cool to near the glass transition temperature. It was then immediately placed in an annealing furnace and held at about the glass transition temperature for about 30 minutes, after which it was slowly cooled at a cooling rate of −30° C./hour for 4 hours, and then allowed to cool to room temperature in the furnace to obtain the optical glasses No. 001 to 118 shown in the table below.
The physical properties of the optical glass thus obtained are shown in the following table.
The physical properties of the optical glasses were measured by the methods described below.

<Evaluation of physical properties of optical glass>
(1) Refractive index nd Abbe number vd
The refractive index nd and Abbe number vd of the obtained glass were measured by the refractive index measurement method specified by the Japan Optical Glass Industry Association.

(2) Glass transition temperature Tg
The glass was thoroughly crushed in a mortar to prepare a sample, and a platinum cell was used as a sample container. The glass transition temperature Tg was measured at a heating rate of 10° C./min using a differential scanning calorimeter (DSC8271) manufactured by Rigaku Corporation.

(3) Specific Gravity Specific gravity was measured by Archimedes' method.

(4) Coloring degree λ ₅ , λ ₇₀
A glass sample having a thickness of 10±0.1 mm and two optically polished flat surfaces facing each other was used to measure the spectral transmittance T (%) using a spectrophotometer. ) was defined as λ ₅ , and the wavelength (nm) at which T was 70% was defined as λ ₇₀ .

[Example 2]
Glass gobs for press molding were prepared using the various glasses obtained in Example 1. The glass gobs were heated and softened in the atmosphere and press molded in a press mold to prepare lens blanks (optical element blanks). The prepared lens blanks were removed from the press mold, annealed, and machined, including polishing, to prepare spherical lenses made of the various glasses prepared in Example 1.

[Example 3]
A desired amount of the molten glass produced in Example 1 was press molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and subjected to mechanical processing including polishing to produce a spherical lens made of the various glasses produced in Example 1.

[Example 4]
The molten glass produced in Example 1 was solidified to produce a glass lump (optical element blank), which was then annealed and machined, including polishing, to produce spherical lenses made of the various glasses produced in Example 1.

[Example 5]
The spherical lenses produced in Examples 2 to 4 were bonded to spherical lenses made of other types of glass to produce cemented lenses. The cemented surfaces of the spherical lenses produced in Examples 2 to 4 were convex, and the cemented surfaces of the spherical lenses made of other types of glass were concave. The above two cemented surfaces were produced so that the absolute values of the radii of curvature were equal to each other. An ultraviolet-curing adhesive for bonding optical elements was applied to the cemented surfaces, and the two lenses were bonded together with their cemented surfaces facing each other. Thereafter, ultraviolet light was irradiated onto the adhesive applied to the cemented surfaces through the spherical lenses produced in Examples 2 to 4 to solidify the adhesive.
A cemented lens was produced in the manner described above. The cemented lens had a sufficiently high bonding strength and exhibited a sufficient level of optical performance.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.
For example, by subjecting the above-mentioned exemplary glass compositions to compositional adjustments as described in the specification, an optical glass according to one aspect of the present invention can be obtained.
Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges.

Claims (12)

In the glass composition based on oxides expressed in mole percent,
_SiO2 content is 1.00% or more and 30.00% or less,
_B2O3 content is 1.00% or more and 40.00% or less _;
La2O3 content _is 5.00% or more and 40.00% or less,
_Gd2O3 content is 0.00% or more and 3.50% or less _{;
The Y2O3} content is 0.50% or more and 20.00% or less,
_TiO2 content is 5.00% or more and 30.00% or less,
_ZrO2 content is 0.00% or more and 20.00% or less;
The Nb ₂ O ₅ content is 0.00% or more and 20.00% or less,
The total content of Gd ₂ O ₃ and Ta ₂ O ₅ (Gd ₂ O ₃ + Ta ₂ O ₅ ) is 0.00% or more and 3.50% or less;
The total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is 26.50% or more;
The total content of TiO ₂ , ZrO ₂ and Nb ₂ O ₅ (TiO ₂ +ZrO ₂ +Nb ₂ O ₅ ) is 23.00% or more and 36.00% or less;
the total content of alkaline earth metal oxide RO and alkali metal oxide R ₂ O (RO + R ₂ O) is 3.50% or more;
the molar ratio of the Gd ₂ O ₃ content to the SiO ₂ content (Gd ₂ O ₃ /SiO ₂ ) is 0.00 or more and 0.23 or less;
the molar ratio of _{the B2O3} content to the _SiO2 content ( _B2O3 / _SiO2 ) is 0.80 or more and 1.56 or less _;
The molar ratio of the _SiO2 content to _{the La2O3} content ( _SiO2 / _La2O3 ) is 0.87 or less;
a molar ratio of the _Y2O3 content to _{the B2O3 content} ( _Y2O3 / _B2O3 ) of 0.15 or more _and 0.34 or less _, and _a molar ratio of the _TiO2 content to the _B2O3 content ( _TiO2 / _{B2O3 )} of 0.70 or more and 1.10 or less _;
Optical glass. 2. The optical glass according to claim 1, having _{an Al2O3} content of 0.00% or more and 2.00% or less. 2. The optical glass according to claim 1, _{wherein the Nb2O5 content} is 0.10% or more and 20.00% or less. 2. The optical glass according to claim 1, wherein the _WO3 content is 0.00% or more and 0.40% or less. _{2. The optical glass} according to claim 1, wherein the total content of _La2O3 , _{Gd2O3 ,} and _{Y2O3 ( La2O3} + _Gd2O3 + _Y2O3 ) is 26.50% _{or more} and 35.00% or less. 2. The optical glass according to claim 1, wherein the combined content of alkaline earth metal oxide RO and alkali metal oxide _R2O (RO+ _R2O ) is 3.50% or more and 10.50% or less. 2. The optical glass according to claim ₁ , _wherein the molar ratio of _{the Y2O3 content to the B2O3 content ( Y2O3} / _B2O3 ) is 0.17 or _more and 0.34 or less. 2. The optical glass according to claim 1, wherein the molar ratio of _{the B2O3} content to the _SiO2 content ( _B2O3 / _SiO2 ) is 1.20 _or more and 1.56 or less. 2. The optical glass according to claim 1, wherein the molar ratio of _{the SiO2 content to the La2O3 content ( SiO2} / _La2O3 ) is 0.50 or more and 0.87 or _less . _2. The optical glass according to claim 1, _wherein the combined content of _Gd2O3 and _Ta2O5 ( _Gd2O3 + _Ta2O5 ) is 0.00% or _more and 2.50% or _less . The Al ₂ O ₃ content is 0.00% or more and 2.00% or less,
The Nb ₂ O ₅ content is 0.10% or more and 20.00% or less,
The _WO3 content is 0.00% or more and 0.40% or less,
The total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is 26.50% or more and 35.00% or less,
the total content (RO+ _R2O ) of alkaline earth metal oxide RO and alkali metal oxide _R2O is 3.50% or more and 10.50% or less;
The molar ratio of the _Y2O3 content to _{the B2O3 content} ( _{Y2O3 /B2O3 )} is 0.17 _or more and 0.34 or less _,
The molar ratio of _{the B2O3} content to the _SiO2 content ( _B2O3 / _SiO2 ) is 1.20 or more and 1.56 or less _;
2. The optical glass according to claim ₁ , wherein the molar ratio of the _{SiO2 content to the La2O3 content} ( _SiO2 / _La2O3 ) is from 0.50 to _0.87 , and the total content of _{Gd2O3 and Ta2O5 ( Gd2O3} + _{Ta2O5 )} is from 0.00% to _2.50 %. An optical element made of the optical glass according to any one of claims 1 to 11.