JP7668751B2 - Optical Glass and Optical Elements - Google Patents

Description

The present invention relates to optical glass and optical elements having desired optical properties.

Many surveillance and security cameras are equipped with night vision capabilities, and their imaging optical systems require imaging performance in the infrared wavelength range. In general, imaging performance in the infrared wavelength range is not required for optical systems such as single-lens reflex and mirrorless cameras, which place emphasis on imaging performance in the visible short wavelength range.

To correct higher-order chromatic aberration, two types of lenses may be combined. For example, a convex lens and a concave lens, or a low-dispersion lens and a high-dispersion lens may be combined. It is desirable that the difference between the Abbe numbers of these two types of lenses is large, and that the difference in the partial dispersion ratio in each wavelength range is small.

Of the two types of lenses mentioned above, fluorophosphate glass, which has low dispersion and anomalous partial dispersion, may be used as one of the lenses. Fluorophosphate glass, which has low dispersion and anomalous partial dispersion, often has a larger Abbe number νd and a larger partial dispersion ratio PC,t in the infrared wavelength range than the lens used in combination with it. Therefore, when improving imaging performance in the near-infrared range, the glass used as the other lens to be combined with the fluorophosphate glass lens is required to have an Abbe number νd smaller than that of the fluorophosphate glass and a PC,t as close as possible to the value of the fluorophosphate glass, that is, a relatively large ΔPC,t is required. When improving imaging performance in the visible short wavelength range, the glass used as the other lens to be combined with the fluorophosphate glass lens is required to have a relatively small ΔPg,F for the same reason.

In high-dispersion glass, when the content of glass components that contribute to high dispersion in the glass composition is increased to decrease the Abbe number νd, the partial dispersion ratio Pg,F in the visible short wavelength region typically increases, and the partial dispersion ratio PC,t in the infrared wavelength region decreases. In lenses made of such high-dispersion glass, the difference between PC,t and that of the above-mentioned fluorophosphate glass becomes large, so chromatic aberration in the visible long wavelength region cannot be sufficiently corrected, making them unsuitable, particularly as lenses for use in night vision cameras.

Patent Documents 1 and 2 focus on anomalous partial dispersion and propose optical glass with dispersion within a specified range, but do not pay any attention to the partial dispersion ratio PC,t in the infrared wavelength range.

Therefore, there is a demand for lenses made of glass with a relatively high PC,t to be combined with fluorophosphate glass lenses in order to correct high-order chromatic aberrations across the near-infrared wavelength range.

Japanese Patent Application Publication No. 10-130033 JP 2017-154963 A

The present invention was made in consideration of these circumstances, and aims to provide optical glass and optical elements with a relatively high partial dispersion ratio PC,t in the infrared wavelength range. With this objective in mind, the researchers searched for glass that would not excessively decrease the partial dispersion ratio PC,t even when highly dispersed, and as a result, they completed the present invention.

The gist of the present invention is as follows.
(1) the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [ ^Nb5 + + ^Ti4 + + ^Ta5+ + ^W6 + + Bi3 ⁺ ] is 6.5 cation% or more;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
Contains substantially no Pb or As,
PC,t satisfies the following formula [2-2],
PC, t≧0.5711+0.004667×νd…[2-2]
An oxide optical glass that satisfies one or more of the following (I) to (IV):
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

(2) the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [ ^Nb5 + + ^Ti4 + + ^Ta5+ + ^W6 + + Bi3 ⁺ ] is 6.5 cation% or more;
the cation ratio [B3 ⁺ /( ^Si4 ++B3 ⁺ )] of the content of B3 ⁺ to the total content of Si4 ⁺ and B3 ⁺ is 0.41 or more and less than 1;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
Contains substantially no Pb or As,
An oxide optical glass that satisfies one or more of the following (I) to (IV):
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

(3) As a glass component,
Contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ ;
Contains one or more selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ ;
An oxide optical glass in which ΔPg,F and ΔPc,t satisfy the following (i) or (ii):
(i) When ΔPg,F is greater than −0.0037, ΔPc,t ≧ 2.875 × ΔPg,F + 0.031.
(ii) When ΔPg,F is equal to or less than −0.0037, ΔPc,t ≧ 4.750 × ΔPg,F + 0.038.

(4) As a glass component,
Contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ ;
Contains one or more selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ ;
An oxide optical glass, wherein P C,t satisfies the following formula [2-1]:
PC, t≧0.5661+0.004667×νd…[2-1]

(5) The oxide optical glass according to (4), in which Pg and F satisfy the following formula [1-1]:
Pg, F≦0.6463-0.001802×νd… [1-1]

(6) The optical glass according to any one of (1) to (5), in which the cation ratio of the total content of Nb5 ⁺ and ^{Ti4 +} to the total content of Nb5 ⁺ , Ti4 ⁺ , ^{W6 +} , and Bi3+ [( ^Nb5 + + ^Ti4+ )/(Nb5 ⁺ + Ti4+ + ^W6 + + ^Bi3+ )] is 0.5 or more.

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

The present invention provides optical glass and optical elements that have a relatively high partial dispersion ratio PC,t in the infrared wavelength range.

In an embodiment of the present invention, the glass composition of the optical glass is expressed in cation % unless otherwise specified. Cation % is the molar percentage when the total content of all cationic components is 100%. The content and total content of glass components are based on cation % unless otherwise specified, and "%" means "cation %". In this specification and the present invention, a content of 0% of a component means that the component is substantially not contained, and it is acceptable for the component to be contained at an unavoidable impurity level.

The anion % is the molar percentage when the total content of all anion components is 100%.

The valence of the cationic component (e.g., the valence of B3 ⁺ is +3, the valence of Si4 ⁺ is +4, and the valence of La3 ⁺ is +3) is a value determined by convention, and is the same as when B, _Si , and La as glass components are expressed on an oxide basis, such as _B2O3 , _SiO2 , and _{La2O3 .} Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of the cationic component. In addition, the valence of the anionic component (e.g., the valence of ^O2- is -2) is also a value determined by convention, and is the same as when glass components on an oxide basis are expressed on an oxide basis, such as _{B2O3 , SiO2} , _{and La2O3} . Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of the anionic component.

The content of glass components can be quantified by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). In this specification and the present invention, a content of 0% of a component means that the component is substantially not contained, and it is acceptable for the component to be present at an unavoidable impurity level.

In this specification, the thermal stability and reheating stability of glass both refer to the resistance to crystal precipitation in the glass. In particular, thermal stability refers to the resistance to crystal precipitation when molten glass solidifies, and reheating stability refers to the resistance to crystal precipitation when solidified glass is reheated, such as during reheat pressing.

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

The optical glass of the present invention will be described below as a first embodiment, a second embodiment, a third embodiment, and a fourth embodiment. In the first embodiment, the optical glass of the present invention will be described in terms of the glass composition and the partial dispersion ratio PC,t shown as a function of the Abbe number νd. In the second embodiment, the optical glass of the present invention will be described in terms of the glass composition. In the third embodiment, the optical glass of the present invention will be described by showing the relationship between ΔPC,t and ΔPg,F as a function of ΔPg,F. In the fourth embodiment, the optical glass of the present invention will be described by showing the partial dispersion ratio PC,t as a function of the Abbe number νd.

First embodiment The oxide optical glass according to the first embodiment is
the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [ ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ ] is 6.5% or more;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
Contains substantially no Pb or As,
PC,t satisfies the following formula [2-2],
PC, t≧0.5711+0.004667×νd…[2-2]
One or more of the following (I) to (IV) are satisfied.
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

In the optical glass according to the first embodiment, the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , ^W6+ , and ^Bi3+ [ ^Nb5 + + ^Ti4 + + ^Ta5+ + ^W6+ + Bi3 ⁺ ] is 6.5% or more. The lower limit of the total content is preferably 7%, 7.5%, 8%, and 8.5%, in that order. The upper limit of the total content is preferably 30%, and more preferably 20%, 15%, 12%, 11.5%, 11%, 10.5%, and 10%, in that order. By keeping the total content within the above range, a high refractive index and a desired Abbe number vd can be maintained.

In the optical glass according to the first embodiment, the cation ratio [(Li ⁺ + Na ⁺ + K ⁺ )/(Li ⁺ + Na ⁺ + K ⁺ + Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ is 0.55 or more. The lower limit of the cation ratio is preferably 0.75, and more preferably 0.80, 0.85, and 0.90 in that order. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.98, 0.96, and 0.94 in that order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased, the meltability of the glass can be improved, and the viscosity of the molten glass can be reduced to improve the moldability. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the first embodiment, the cation ratio [Zr4 ⁺ /(Nb5 ⁺⁺ Ti4 ⁺⁺ Ta5 ^{++ W6} ++Bi3 ⁺ )] of the content of Zr4 ⁺ to the total content of Nb5+, ^Ti4+ , ^{Ta5 +} , W6+, and ^{Bi3 +} is 0.4 or more. The lower limit of the cation ratio is preferably 0.42, and more preferably 0.44, 0.46, 0.48, and 0.50 in this order. The upper limit of the cation ratio is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.65, 0.6, and 0.55 in this order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased and high dispersion can be maintained.

In the optical glass according to the first embodiment, the cation ratio [(Si4 ^{++ B3} ++Li ⁺⁺ Na ⁺⁺ K+ ^{Zr4 +} )/( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺⁾ ] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of Nb5+, ^Ti4 +, ^Ta5 +, ^{W6 +} , and Bi3 ⁺ is 8.6 or more. The lower limit of the cation ratio is preferably 8.8, and more preferably 9.0, 9.2, 9.4, 9.6, and 9.8 in this order. The upper limit of the cation ratio is preferably 20, and more preferably 18, 16, 14, 13, 12, and 11 in this order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased, and the Abbe number can be adjusted.

The optical glass according to the first embodiment does not substantially contain Pb and As, which are components that are of concern for their environmental impact. That is, the content of each of Pb ions and As ions is 0%. Similarly to Pb and As, Th is also a component that is of concern for its environmental impact. Therefore, the content of Th ions is preferably 0 to 0.1%, and may be 0 to 0.05%, or 0 to 0.01%. The content of Th ions is preferably 0%. That is, it is preferable that Th is not substantially contained. Note that the Pb ions include Pb ions with different valences in addition to Pb ²⁺ . The As ions and Th ions also include ions with different valences.

In the optical glass according to the first embodiment, the partial dispersion ratio PC,t satisfies the following formula [2-2].
PC, t≧0.5711+0.004667×νd…[2-2]
It is more preferable that the partial dispersion ratio PC,t satisfies the following formula [2-3], and more preferably satisfies the following formula [2-4], the following formula [2-5], the following formula [2-6], the following formula [2-7], and the following formula [2-8] in that order.
PC, t≧0.5731+0.004667×νd…[2-3]
PC, t≧0.5751+0.004667×νd…[2-4]
PC, t≧0.5771+0.004667×νd…[2-5]
PC, t≧0.5791+0.004667×νd… [2-6]
PC, t≧0.5811+0.004667×νd…[2-7]
PC, t≧0.5831+0.004667×νd…[2-8]

When the partial dispersion ratio PC,t satisfies the above formula, the optical element made of the optical glass according to the first embodiment can effectively correct chromatic aberration over a wide wavelength range.

The optical glass according to the first embodiment satisfies one or more of the following (I) to (IV).
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

That is, in the optical glass according to the first embodiment, in the case of (I) above, the cation ratio [( ^{Li +} Na ⁺ K ⁺ )/(Si ⁴⁺ + B ³⁺ )] of the total content of Li ⁺ , Na + , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.85 or less. In the case of (I) above, the upper limit of the cation ratio can be 0.80, 0.75, 0.70, 0.65, 0.60, or 0.55. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, in the case of (II) above, the cation ratio [(Li ⁺ Na ^{+ K + )} /(Si ⁴⁺ + B ³⁺ )] of the total content of Li ⁺ , Na + , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.97 or less. In the case of (II) above, the upper limit of the cation ratio can be 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, or 0.55. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, in the case of (II) above, the cation ratio [(Li ⁺ Na ⁺ Mg ²⁺ + Ca ²⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr 2+ + Ba ²⁺ + Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , Mg ²⁺ , and Ca ²⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ^{2+ ,} and Zn ²⁺ can be 0.75 or more. In the case of (II) above, the lower limit of the cation ratio can be 0.77, 0.79, 0.81, 0.83, 0.85, 0.87, or 0.89. The upper limit of the cation ratio is preferably 1, and more preferably 0.99, 0.98, and 0.95 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be within the above range.

In the optical glass according to the first embodiment, in the case of (III), the cation ratio [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.46 or more. In the case of (III), the lower limit of the cation ratio can be 0.50, 0.51, 0.53, 0.55, 0.57, or 0.59. The cation ratio is preferably less than 1, and the upper limit is more preferably 0.90, 0.85, 0.80, 0.75, 0.70, and 0.65 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable to set the cation ratio within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the chemical durability of the glass may decrease.

In the optical glass according to the first embodiment, in the case of (IV) above, the cation ratio [(Li ⁺ Na ⁺ K ⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr ^{2+ + Ba 2+ +} Zn ²⁺ )] of the total content of Li ⁺ , Na ^{+ ,} and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ can be 0.75 or more. In the case of (IV) above, the lower limit of the cation ratio can be 0.80, 0.85, or 0.90. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.98, 0.96, and 0.94 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the moldability, it is preferable that the cation ratio is within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the first embodiment, in the case of (IV) above, the cation ratio [( ^B3+ + Li ⁺ ) / (Si4 ⁺ + Na ⁺ + K ⁺ )] of the total content of B3 ⁺ and Li ⁺ to the total content of Si4 ⁺ , Na ⁺ , and K ⁺ can be 0.31 or more. The lower limit of the cation ratio can be 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, or 1.20. The upper limit of the cation ratio is preferably 10, and more preferably 9, 8, 7, 6, 5, 4, 3, 2, and 1.8 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the cation ratio is within the above range.

The following are non-limiting examples of the contents and ratios of glass components other than those described above in the optical glass according to the first embodiment.

The optical glass according to the first embodiment preferably contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ as glass components.

In the optical glass according to the first embodiment, the lower limit of the Si ⁴⁺ content is preferably 5%, more preferably 7%, 9%, 11%, 13%, 15%, 17%, 19%, and 21% in this order. The upper limit of the Si ⁴⁺ content is preferably 50%, more preferably 40%, 35%, 32%, 30%, 28%, 26%, and 24% in this order. Si ⁴⁺ is a glass network forming component. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving the chemical durability, it is preferable that the Si ⁴⁺ content is within the above range. If the Si ⁴⁺ content is too small, the partial dispersion ratio PC,t in the infrared wavelength range may decrease, and the thermal stability and chemical durability of the glass may decrease. If the Si ⁴⁺ content is too large, the meltability of the glass may decrease, and the viscosity of the molten glass may increase, causing the moldability to deteriorate.

In the optical glass according to the first embodiment, the lower limit of the content of B ³⁺ is preferably 10%, more preferably 15%, 20%, 25%, 28%, 30%, and 32% in this order. The upper limit of the content of B ³⁺ is preferably 60%, more preferably 55%, 50%, 45%, 40%, 38%, and 36% in this order. B ³⁺ is a glass network forming component. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the content of B ³⁺ is within the above range. If the content of B ³⁺ is too small, the partial dispersion ratio PC,t in the infrared wavelength region may decrease, and the thermal stability of the glass may decrease. If the content of B ³⁺ is too large, the chemical durability of the glass may decrease.

In the optical glass according to the first embodiment, the lower limit of the content of Zr4 ⁺ is preferably 0.1%, more preferably 1%, 2%, 2.5%, 3%, 3.5%, 4%, and 4.5% in that order. The upper limit of the content of Zr4 ⁺ is preferably 20%, more preferably 15%, 10%, 8%, 6%, and 5% in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the content of Zr4 ⁺ is within the above range. If the content of Zr4 ⁺ is too small, the chemical durability may decrease. If the content of ^Zr4+ is too large, the liquidus temperature LT may increase and the stability during reheating may decrease.

In the optical glass according to the first embodiment, the lower limit of the content of Nb ⁵⁺ is preferably 0.1%, more preferably 1%, 3%, 5%, 7%, 7.5%, and 8%, in that order. The upper limit of the content of Nb ⁵⁺ is preferably 30%, more preferably 20%, 15%, 12%, 11.5%, 11%, 10.5%, and 10%, in that order. By setting the content of Nb ⁵⁺ within the above range, high dispersion can be maintained while suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range. If the content of Nb ⁵⁺ is too small, high dispersion may not be maintained. If the content of Nb ⁵⁺ is too large, the partial dispersion ratio PC,t in the infrared wavelength range may decrease.

The optical glass according to the first embodiment preferably contains, as a glass component, one or more elements selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ . The optical glass according to the first embodiment more preferably contains Li ⁺ and Na ⁺ .

In the glass according to the first embodiment, the lower limit of the Li ⁺ content is preferably 0%, more preferably 5%, 10%, and 15% in that order. The upper limit of the Li ⁺ content is preferably 50%, more preferably 40%, 30%, and 25% in that order. Li ⁺ is a component that contributes to lowering the viscosity of the glass, and among alkali metals, it has a large effect of increasing the partial dispersion ratio PC,t in the infrared wavelength range. If the Li ⁺ content is too high, the stability during reheating may decrease. If the Li ⁺ content is too low, the viscosity of the glass may increase.

In the glass according to the first embodiment, the lower limit of the content of Na ⁺ is preferably 0%, more preferably 2%, 4%, 6%, and 8% in this order. The upper limit of the content of Na ⁺ is preferably 50%, more preferably 40%, 30%, 25%, 20%, 15%, and 10% in this order. Na ⁺ is a component that contributes to the low viscosity of glass, similar to Li ⁺ . If the content of Na ⁺ is too high, the stability during reheating may decrease. If the content of Na ⁺ is too low, the viscosity of glass may increase.

In the optical glass according to the first embodiment, the upper limit of the content of K ⁺ is preferably 50%, more preferably 40%, 30%, 25%, 20%, 15%, 10%, and 5% in this order. The lower limit of the content of K ⁺ is preferably 0%, more preferably 1%, 2%, and 3% in this order. The content of K ⁺ may be 0%. K ⁺ has the function of lowering the liquidus temperature and improving the thermal stability of the glass. On the other hand, if the content of K ⁺ increases, the chemical durability, weather resistance, and stability during reheating decrease. Therefore, the content of K ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the lower limit of the total content of Li ⁺ , Na ⁺ , and K ⁺ [ ^Li + ^Na +K ⁺ ] is preferably 1%, more preferably 5%, 10%, 15%, 20%, and 25% in that order. The upper limit of the total content [ ^{Li +} Na+K ⁺ ] is preferably 60%, more preferably 50%, 40%, 35%, and 30% in that order. From the viewpoint of suppressing a decrease in stability during reheating, it is preferable that the total content is within the above range.

In the optical glass according to the first embodiment, the upper limit of the Al ³⁺ content is preferably 20%, more preferably 10%, 5%, 2%, and 1% in that order. The lower limit of the Al ³⁺ content is preferably 0%, more preferably 0.1%, 0.2%, and 0.3% in that order. The Al ³⁺ content may be 0%. When an appropriate amount of Al ³⁺ is contained, it has the effect of suppressing phase separation of the glass. On the other hand, from the viewpoint of maintaining the thermal stability of the glass, it is preferable that the Al ³⁺ content is within the above range.

In the optical glass according to the first embodiment, the upper limit of the P5 ⁺ content is preferably 20%, more preferably 10%, 5%, and 3%, in that order. The lower limit of the ^{P5 +} content is preferably 0.1%, more preferably 0.5%, 0.8%, and 1%, in that order. ^{The P5+} content may be 0%. By keeping the P5+ content within the above range, the thermal stability of the glass can be maintained.

In the optical glass according to the first embodiment, the upper limit of the Cs ⁺ content is preferably 20%, and more preferably 15%, 10%, and 5% in that order. The lower limit of the Cs ⁺ content is preferably 0%. The Cs ⁺ content may be 0%.

Cs ⁺ has the function of improving the thermal stability of glass, but if the content is too high, there is a risk of reducing chemical durability and weather resistance. Therefore, the content of Cs ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Mg2 ⁺ content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1%, in that order. The lower limit of the Mg2 ⁺ content is preferably 0%. ^{The Mg2+} content may be 0%.

Among alkaline earth metals, Mg ²⁺ is a component that increases the partial dispersion ratio PC,t in the infrared wavelength region. However, if the content of Mg ²⁺ increases, the high dispersion is impaired, and the thermal stability and devitrification resistance of the glass may be reduced. Therefore, the content of Mg ²⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Ca2 ⁺ content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. The lower limit of the Ca2 ⁺ content is preferably 0%. ^{The Ca2+} content may be 0%.

Among alkaline earth metals, Ca2 ⁺ is a component that increases the partial dispersion ratio PC,t in the infrared wavelength region. However, if the content of Ca2 ⁺ increases, the high dispersion is impaired, and the thermal stability and devitrification resistance of the glass may be reduced. Therefore, the content of Ca2 ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Sr2 ⁺ content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1%, in that order. The lower limit of the Sr2 ⁺ content is preferably 0%. ^{The Sr2+} content may be 0%.

Sr2 ⁺ is a component that increases the refractive index among alkaline earth metals. However, if the content of Sr2 ⁺ is large, the high dispersion is impaired and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. Therefore, the content of Sr2 ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Ba2 ⁺ content is preferably 20%, and more preferably 10%, 9%, 8%, 7%, 6%, 5%, 4%, and 3% in that order. The lower limit of ^{the Ba2+} content is preferably 0%, and more preferably 0.5%, 1.0%, and 1.5% in that order. ^{The Ba2+} content may be 0%.

Ba2 ⁺ is a component that increases the refractive index and at the same time lowers the liquidus temperature and increases the stability of the glass. However, if the content of Ba2 ⁺ is too high, the high dispersion is impaired and the partial dispersion ratio PC,t in the infrared wavelength range may decrease. If the content of Ba2 ⁺ is too low, the refractive index nd may decrease and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the content of Ba2 ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Zn2 ⁺ content is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. The lower limit of the Zn2 ⁺ content is preferably 0%, and more preferably 0.1%, 0.5%, and 0.7% in that order. ^{The Zn2+} content may be 0%.

Zn2 ⁺ is a glass component that has the function of improving the thermal stability of glass. However, if the content of Zn2 ⁺ is too high, the specific gravity may increase and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical constants, the content of Zn2 ⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the content of La ³⁺ is preferably 20%, more preferably 10%, 5%, 4%, and 3% in that order. The lower limit of the content of La ³⁺ is preferably 0%, more preferably 1% and 2% in that order. The content of La ³⁺ may be 0%. The refractive index nd can be increased by introducing a certain amount of La ³⁺ . However, if the content of La ³⁺ becomes too large, the thermal stability of the glass decreases, and the glass becomes more likely to devitrify during production. In addition, there is a risk that the high dispersion is impaired, and the partial dispersion ratio PC,t in the infrared wavelength region decreases. Therefore, it is preferable that the content of La ³⁺ is within the above range.

In the glass according to the first embodiment, the content of Gd ³⁺ is preferably 2% or less. The lower limit of the content of Gd ³⁺ is preferably 0%. If the content of Gd ³⁺ is too high, the thermal stability of the glass decreases. If the content of Gd ³⁺ is too high, the specific gravity of the glass increases, which is undesirable. There is also a risk of an increase in raw material costs. Therefore, from the viewpoint of suppressing an increase in the specific gravity while maintaining good thermal stability of the glass, the content of Gd ³⁺ is preferably within the above range.

In the glass according to the first embodiment, the upper limit of the Y ³⁺ content is preferably 20%, more preferably 10%, 5%, 4%, and 3% in that order. The lower limit of the Y ³⁺ content is preferably 0%, more preferably 1%, and 2% in that order. The Y ³⁺ content may be 0%.

By introducing a certain amount of Y ³⁺ , the refractive index nd can be increased. However, if the content of Y ³⁺ is too high, the thermal stability of the glass decreases, and the glass is likely to devitrify during production. In addition, there is a risk of losing high dispersion. Therefore, from the viewpoint of suppressing the decrease in the thermal stability of the glass, the content of Y ³⁺ is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the Ti4 ⁺ content is preferably 20%, more preferably 15%, 10%, 8%, 6%, and 4% in that order. The lower limit of the Ti4 ⁺ content is preferably 0%, more preferably 1%, 2%, and 3% in that order. ^{The Ti4+} content may be 0%. By setting ^{the Ti4+} content within the above range, it is possible to realize the desired optical constants and suppress an increase in specific gravity.

In the optical glass according to the first embodiment, the upper limit of the Ta5 ⁺ content is preferably 20%, and more preferably 15%, 10%, 9%, 8%, and 6% in that order. The lower limit of the Ta5 ⁺ content is preferably 0%, and more preferably 1%, 2%, 3%, and 4% in that order. ^{The Ta5+} content may be 0%.

Ta5 ⁺ is a component that gives the glass high refraction and low dispersion, and increases the partial dispersion ratio PC,t in the infrared wavelength region. On the other hand, if the content of Ta5 ⁺ increases, the raw material cost increases. In addition, there is a risk of the specific gravity increasing. Therefore, it is preferable that the content of Ta5 ⁺ is within the above range.

In the optical glass according to the first embodiment, the upper limit of the content of W6 ⁺ is preferably 20%, and more preferably 15%, 10%, 8%, 6%, 4%, 2%, 1%, 0.5%, and 0.1% in that order. The lower limit of the content of ^W6+ is preferably 0%. The content of W6 ⁺ may be 0%. From the viewpoints of increasing the transmittance, suppressing a decrease in the partial dispersion ratio PC,t in the infrared wavelength range, and reducing the specific gravity, it is preferable that the content of W6 ⁺ is within the above range.

In the optical glass according to the first embodiment, the upper limit of the Bi ³⁺ content is preferably 20%, more preferably 15%, 10%, 8%, and 6%, in that order. The lower limit of the Bi ³⁺ content is preferably 0%, more preferably 1%, 2%, 3%, 4%, and 5%, in that order. The Bi ³⁺ content may be 0%. From the viewpoints of increasing the transmittance and reducing the specific gravity, and from the viewpoint of reducing damage to platinum manufacturing equipment, it is preferable that the Bi ³⁺ content be within the above range.

In the glass according to the first embodiment, the content of Sc ³⁺ is preferably 2% or less. The lower limit of the content of Sc ³⁺ is preferably 0%.

In the glass according to the first embodiment, the content of Hf ⁴⁺ is preferably 2% or less. The lower limit of the content of Hf ⁴⁺ is preferably 0%.

Sc ³⁺ and Hf ⁴⁺ have the effect of increasing the dispersibility of the glass, but are expensive components, so the contents of Sc ³⁺ and Hf ⁴⁺ are preferably within the above ranges.

In the glass according to the first embodiment, the content of Lu ³⁺ is preferably 2% or less. The lower limit of the content of Lu ³⁺ is preferably 0%.

Lu ³⁺ has the function of increasing the dispersibility of the glass, but because of its large molecular weight, it is also a glass component that increases the specific gravity of the glass, so the content of Lu ³⁺ is preferably within the above range.

In the glass according to the first embodiment, the content of Ge ⁴⁺ is preferably 2% or less. The lower limit of the content of Ge ⁴⁺ is preferably 0%.

Ge ⁴⁺ has the function of increasing the high dispersibility of the glass, but is an extremely expensive component among commonly used glass components, and therefore, from the viewpoint of reducing the manufacturing cost of the glass, the content of Ge ⁴⁺ is preferably within the above range.

In the glass according to the first embodiment, the content of Yb ³⁺ is preferably 2% or less. The lower limit of the content of Yb ³⁺ is preferably 0%.

Yb3 ⁺ has a larger molecular weight than La3 ⁺ , Gd3 ⁺ , and Y3 ⁺ , and therefore increases the specific gravity of the glass. If the content of Yb3 ⁺ is too high, the thermal stability of the glass decreases. From the viewpoint of preventing the decrease in the thermal stability of the glass and suppressing the increase in the specific gravity, the content of Yb3 ⁺ is preferably within the above range.

In the glass according to the first embodiment, the upper limit of each of the Cu ion and Ag ion contents is preferably 1%, and more preferably 0.5%, 0.2%, 0.1%, 0.05%, and 0.03%, in that order. The lower limit of each of the Cu ion and Ag ion contents is preferably 0%. From the viewpoint of suppressing coloration of the glass, it is preferable that each of the Cu ion and Ag ion contents is within the above range. The Cu ions and Ag ions each include ions with different valences.

In the glass according to the first embodiment, the lower limit of the cation ratio [(Nb5 ⁺ + Ti4 ⁺ )/(Nb5 ^{+ + Ti4 +} + ^W6+ + ^{Bi3 +} )] of the total content of Nb5+ and Ti4+ to the total content of Nb5 ⁺ , ^Ti4 +, ^W6+ , and ^Bi3+ is preferably 0.5, more preferably 0.6, 0.7, 0.8, 0.9, and 0.95 in this order. The upper limit of the cation ratio is preferably 1, more preferably 0.99, 0.98, and 0.97 in this order. From the viewpoint of suppressing the decrease in the partial dispersion ratio PC,t in the infrared wavelength region, the cation ratio is preferably within the above range.

In the optical glass according to the first embodiment, the lower limit of the total content of Si ⁴⁺ and B ³⁺ [Si ⁴⁺ +B ³⁺ ] is preferably 20%, more preferably 25%, 30%, 35%, 40%, 45%, 50%, 52%, 54%, and 56% in this order. The upper limit of the total content is preferably 80%, more preferably 75%, 70%, 65%, and 60% in this order. By setting the total content within the above range, the partial dispersion ratio PC,t in the infrared wavelength range can be increased and the thermal stability of the glass can be maintained. If the total content is too small, the partial dispersion ratio PC,t in the infrared wavelength range may decrease, and the thermal stability and chemical durability of the glass may not be maintained. If the total content is too large, the viscosity of the molten glass may increase, and the moldability may deteriorate. In addition, the refractive index may decrease.

In the optical glass according to the first embodiment, the lower limit of the total content of Si4 ⁺ , B3 ⁺ , and Al3 ⁺ [ ^Si4 ++ ^B3 ++Al3 ⁺ ] is preferably 20%, more preferably 25%, 30%, 35%, 40%, 45%, 50%, 52%, 54%, and 56% in this order. The upper limit of the total content is preferably 80%, more preferably 75%, 70%, 65%, and 60% in this order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range and maintaining the thermal stability and stability during reheating of the glass, it is preferable that the total content is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Li ⁺ / (Li ⁺ + Na ^{+ + K + )] of the content of Li + to the total content of Li + , Na + , and K + is} preferably 1, more preferably 0.95, 0.90, 0.85, 0.80, and 0.75 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, and 0.65 in this order. From the viewpoint of suppressing the decrease in stability during reheating, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Na ⁺ /(Li ⁺ +Na ^{+ +K +)] of the content of Na + to the total content of Li + , Na + , and K + is} preferably 1, and more preferably 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, and 0.35 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.05, 0.10, 0.15, 0.20, and 0.25 in this order. The cation ratio may be 0. From the viewpoint of suppressing the decrease in stability during reheating, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [K ⁺ / (Li ⁺ Na ⁺ + K ⁺ )] of the content of K ⁺ to the total content of Li ⁺ , Na ⁺ , and ^K + is preferably 1, and more preferably 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, 0.25 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.05, 0.10, 0.15 in this order. The cation ratio may be 0. From the viewpoint of suppressing the decrease in stability during reheating, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ [Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ] is preferably 20%, and more preferably 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, and 3% in this order. The lower limit of the total content is preferably 0%, and more preferably 0.3%, 0.6%, 0.9%, 1.0%, 1.2%, 1.5%, 1.7%, and 1.9% in this order. The total content may be 0%. If the total content is too high, the high dispersion may be impaired, and the partial dispersion ratio PC,t in the infrared wavelength region may be reduced. If the total content is too low, the refractive index nd may be reduced, and the thermal stability and devitrification resistance of the glass may be reduced. Therefore, the total content is preferably within the above range.

In the optical glass according to the first embodiment, the upper limit of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ [Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ] is preferably 20%, more preferably 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3% in this order. The lower limit of the total content is preferably 0%, more preferably 0.3%, 0.6%, 0.9%, 1.0%, 1.2%, 1.5%, 1.7%, 1.9% in this order. The total content may be 0%. If the total content is too high, the high dispersion is impaired, and the partial dispersion ratio PC,t in the infrared wavelength region may decrease. On the other hand, if the total content is too small, the refractive index nd decreases, and the thermal stability and devitrification resistance of the glass may decrease. Therefore, the total content is preferably in the above range.

In the glass according to the first embodiment, the upper limit of the total content of La3 ⁺ , Gd3 ⁺ , and ^Y3+ [La3 ⁺ + ^Gd3+ + Y3 ⁺ ] is preferably 20%, and more preferably 10%, 5%, 4%, 3%, 2%, and 1% in that order. The lower limit of the total content is preferably 0%. From the viewpoint of suppressing a decrease in the thermal stability of the glass and from the viewpoint of preventing a decrease in the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the total content is within the above range.

In the optical glass according to the first embodiment, the upper limit of the total content of Nb5 ⁺ and Zr4 ⁺ [Nb5 ⁺ + Zr4 ⁺ ] is preferably 30%, more preferably 25%, 20%, 18%, 16%, and 15% in that order. The lower limit of the total content is preferably 5%, more preferably 7%, 9%, 10%, 11%, and 12% in that order. From the viewpoint of minimizing the decrease in the partial dispersion ratio PC,t in the infrared wavelength region without impairing high dispersion, it is preferable that the total content be within the above range.

In the optical glass according to the first embodiment, the upper limit of the total content of Ta5 ⁺ and Zr4 ⁺ [Ta5 ⁺ + Zr4 ⁺ ] is preferably 20.0%, more preferably 15.0%, 12.0%, 10.0%, 9.5%, 9.0%, 8.5%, 8.0%, 7.5%, 7.0%, 6.5%, 6.0%, 5.5%, 5.0% in this order. The lower limit of the total content is preferably 1.0%, more preferably 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5% in this order. From the viewpoint of maintaining the thermal stability of the glass, it is preferable that the total content is within the above range. If the total content is too small, the chemical durability of the glass may be reduced. If the total content is too large, the thermal stability of the glass may be reduced, and the raw material cost may be increased.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Nb5 ⁺ /(Nb5 ^{++ Ti4++} Ta5 ^{++ W6++} Bi3 ⁺ )] of the content of Nb5 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , ^Ta5 +, ^W6+ , and Bi3 ⁺ is preferably 1, and more preferably 0.99, 0.98, 0.97, 0.96, 0.95, 0.94, 0.93, 0.92, and 0.91 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.5, 0.6, 0.7, 0.8, and 0.9 in this order. The cation ratio may be 1. From the viewpoint of maintaining a high refractive index, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Ta5 ⁺ /(Nb5 ^{++ Ti4} ++ ^{Ta5++ W6} ++Bi3 ⁺ )] of the content of Ta5 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , ^Ta5 +, ^W6+ , and Bi3 ⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of suppressing an increase in raw material costs, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Ti4 ⁺ /(Nb5 ^{++ Ti4} ++ ^{Ta5++ W6} ++Bi3 ⁺ )] of the content of Ti4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , ^Ta5 +, ^W6+ , and Bi3 ⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of maintaining high dispersion and from the viewpoint of suppressing the increase of the partial dispersion ratio Pg,F in the visible short wavelength region, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the lower limit of the total content of Nb5 ⁺ , Zr4 ⁺ , Ti4 ⁺ , Ta5 ⁺ , ^W6+ , and ^Bi3 + [Nb5 ⁺ + ^Zr4 + + ^{Ti4 +} + Ta5+ + ^W6 + + Bi3 ⁺ ] is preferably 5.0%, and more preferably 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, and 13%, in that order. The upper limit of the total content is preferably 20%, and more preferably 19%, 18%, 17%, 16%, and 15%, in that order. From the viewpoint of increasing the refractive index nd and adjusting the Abbe number vd, it is preferable that the total content is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Nb5 ⁺ /(Nb5++ ^Zr4 ++ ^{Ti4 ++} Ta5 ^{++ W6} ++Bi3 ⁺ )] of the content of Nb5 ⁺ to the total content of Nb5 ⁺ , ^Zr4 +, ^Ti4 +, ^Ta5+ , ^W6+ , and Bi3 ⁺ is preferably 0.9, more preferably 0.8, 0.75, and 0.7 in this order. The lower limit of the cation ratio is preferably 0.1, more preferably 0.2, 0.3, 0.4, and 0.45 in this order. From the viewpoint of maintaining high dispersibility, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [Zr4 ⁺ /( ^{Nb5++ Zr4} ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Zr4+, ^Ti4 +, ^{Ta5 +} , ^W6 +, and Bi3 ⁺ is preferably 0.9, more preferably 0.8, 0.7, 0.6, 0.55, 0.5, 0.45, and 0.4 in this order. The lower limit of the cation ratio is preferably 0.01, more preferably 0.10, 0.15, 0.20, 0.25, and 0.30 in this order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region and maintaining high dispersion, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [ ^{Ta5+ /} (Nb5++ ^Zr4 ++ ^Ti4 ++Ta5 ^{++ W6} ++Bi3 ⁺ )] of the content of Ta5 ⁺ to the total content of Nb5 ⁺ , ^Zr4 +, ^Ti4 +, ^Ta5 +, ^W6+ , and Bi3 ⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of suppressing the increase in raw material cost, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [ ^{Ti4+ /} (Nb5++ ^Zr4 ++Ti4 ⁺⁺ Ta5 ^{++ W6} ++Bi3 ⁺ )] of the content of Ti4 ⁺ to the total content of Nb5 ⁺ , ^Zr4 +, ^Ti4 +, ^Ta5 +, ^W6+ , and Bi3 ⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.03, 0.05, and 0.07 in this order. The cation ratio may be 0. From the viewpoint of maintaining high dispersion and from the viewpoint of suppressing the increase of the partial dispersion ratio Pg,F in the visible short wavelength region, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ )/(Si ^{4+ + B 3+ )] of the total content of Mg 2+ , Ca 2+} , Sr ²⁺ , and Ba ²⁺ to the total content of Si ⁴⁺ and B ³⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, 0.1, and 0.08 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.01, 0.02, and 0.03 in this order. The cation ratio may be 0. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )/(Si ⁴⁺ + B ³⁺ )] of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Si ⁴⁺ and B ³⁺ is preferably 0.5, more preferably 0.4, 0.3, 0.2, 0.1, 0.08 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.01, 0.02, 0.03 in this order. The cation ratio may be 0. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [(Li ⁺ Na ⁺⁺ K ^{++ Mg2} ++ ^Ca2 ++ ^Sr2 ++ ^Ba2 ++Zn2 ⁺⁾ /( ^Si4 ++B3 ⁺⁾ ] of the total content of Li ⁺ , Na ^+, K ⁺ , ^Mg2 +, ^Ca2 +, Sr2 ⁺ , Ba2 ⁺ and ^Zn2 + to the total content of Si4 ⁺ and B3 ⁺ is preferably 1.50, and more preferably 1.40, 1.30, 1.20, 1.10, 1.00, 0.90, 0.80, 0.70, 0.60 and 0.55 in that order. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, and 0.45 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(La ³⁺ + Gd ³⁺ + Y ³⁺ )/(Si ⁴⁺ + B ³⁺ )] of the total content of La ³⁺ , Gd ³⁺ , and Y ³⁺ to the total content of Si ⁴⁺ and B ³⁺ is preferably 0.5, and more preferably 0.4, 0.3, 0.2, 0.1, and 0.08 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, and 0.03 in this order. The cation ratio may be 0. From the viewpoint of suppressing the deterioration of the thermal stability of the glass, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Nb5 ^{+Ti4 +} Ta5 ^{+ W6} +Bi3 ⁺ )/(Si4+ ^B3+ )] of the total content of Nb5 ⁺ , ^{Ti4 +} , ^Ta5 +, ^{W6 +} , and Bi3 ⁺ to the total content of Si4 ⁺ and B3+ is preferably 0.50, and more preferably 0.40, 0.35, 0.30, 0.25, 0.20, and 0.18 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.02, 0.04, 0.06, 0.08, 0.10, and 0.12 in this order. From the viewpoint of maintaining a high refractive index and a desired Abbe number νd, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ )/(Li ⁺ + Na + K ⁺ )] of the total content of Mg ²⁺ , ^{Ca 2+ ,} Sr ²⁺ , and Ba ²⁺ to the total content of Li ⁺ , Na ⁺ , and K ⁺ is preferably 0.6, and more preferably 0.5, 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.02, 0.04, and 0.06 in this order. The cation ratio may be 0. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the formability, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )/(Li ^{+ +} Na + K ⁺ )] of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Li ⁺ , Na ⁺ and K ⁺ is preferably 0.6, more preferably 0.5, 0.4, 0.3, 0.2 and 0.1 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.02, 0.04 and 0.06 in this order. The cation ratio may be 0. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength range, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the formability, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(La ³⁺ + Gd ³⁺ + Y ³⁺ )/(Li ⁺ + Na ⁺ + K ⁺ )] of the total content of La ³⁺ , Gd ³⁺ , and Y ³⁺ to the total content of Li ⁺ , Na ⁺ , and K ⁺ is preferably 0.5, more preferably 0.4, 0.3, and 0.2 in this order. The lower limit of the cation ratio is preferably 0, more preferably 0.01, 0.03, and 0.05 in this order. The cation ratio may be 0. From the viewpoint of suppressing the deterioration of the thermal stability of the glass, it is preferable that the cation ratio is within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Nb5 ⁺ Ti4 ⁺ Ta5 ^{+ W6} + ^{Bi3+) /} (Li ⁺ Na ⁺ K ⁺ )] of the total content of Nb5+, Ti4 ⁺ , Ta5 ⁺ , ^{W6+ ,} and Bi3+ to the total content of Li ⁺ , Na ⁺ , and K ⁺ is preferably 0.60, more preferably 0.55, 0.50, 0.45, and 0.40 in this order. The lower limit of the cation ratio is preferably 0.05, more preferably 0.10, 0.15, 0.17, 0.19, 0.21, 0.23, and 0.25 in this order. From the viewpoints of maintaining a high refractive index, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve its moldability, it is preferable that the cation ratio be within the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(Li ⁺ Na ⁺ K ⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na + , ^{K + ,} Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ is preferably 1, and more preferably 0.99, 0.98, 0.97, 0.96, 0.95, and 0.94 in that order. The lower limit of the cation ratio is preferably 0.50, and more preferably 0.55, 0.60, 0.65, 0.70, and 0.75 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be in the above range.

In the glass according to the first embodiment, the upper limit of the cation ratio [(La3 ^{+ Gd3} ++Y3 ⁺⁾ /( ^Nb5 ++ ^Ti4 ++Ta5 ^{++ W6} ++Bi3 ⁺ )] of the total content of La3 ⁺ , Gd3 ⁺ , and Y3 ⁺ to the total content of Nb5 ⁺ , Ti4+, ^Ta5 +, ^{W6 +} , and Bi3 ⁺ is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1 in this order. The lower limit of the cation ratio is preferably 0, and more preferably 0.01, 0.02, 0.03, 0.04, and 0.05 in this order. The cation ratio may be 0. From the viewpoint of preventing a decrease in the thermal stability of the glass and maintaining a high refractive index, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the upper limit of the cation ratio [ ^{B3+ /} (Nb5++Zr4 ^{++ Ti4} ++ ^Ta5 ++ ^W6++ Bi3 ⁺ )] of the content of B3 ⁺ to the total content of Nb5 ⁺ , Zr4+, ^Ti4 +, ^Ta5 +, ^{W6 +} and Bi3+ is preferably 7.0, more preferably 6.0, 5.5, 5.0, 4.5, 4.0, 3.5, ^3.0 in this order. The lower limit of the cation ratio is preferably 1.0, more preferably 1.2, 1.4, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 in this order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the cation ratio is within the above range.

In the optical glass according to the first embodiment, the lower limit of the cation ratio [Zr4 ^+/ (Nb5 ⁺ +Ti4 ⁺ +Ta5 ^{+ +W6 + +} Bi3 ^{+ +} Mg2 ⁺ +Ca2 ⁺ +Sr2 ⁺ +Ba2+ +Zn2 ⁺⁾ ] of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5+, ^W6 +, ^Bi3 +, ^Mg2 +, Ca2 ⁺ , Sr2 ⁺ , ^{Ba2+ ,} and Zn2 ⁺ is preferably 0.17, and more preferably 0.20, 0.25, 0.30, 0.35, 0.37, 0.39, and 0.40 in that order. The upper limit of the cation ratio is preferably 2.00, and more preferably 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, and 0.60 in that order. In order to improve chemical durability, increase the refractive index nd, and maintain high dispersibility, it is preferable to set the cation ratio within the above range. If the cation ratio is too small, the refractive index nd may decrease, and the chemical durability of the glass may decrease. If the cation ratio is too large, the liquidus temperature LT may increase, and the stability during reheating may decrease.

In the optical glass according to the first embodiment, the lower limit of the cation ratio [(Zr4 ⁺ + Ta5 ⁺⁾ /(Nb5 ⁺ + Ti4 ^{+ + W6 + +} Bi3 ^{+ +} Mg2 ⁺ + Ca2 ⁺ + Sr2 ^{+ +} Ba2+ + Zn2 ⁺ )] of the total content of Zr4 ⁺ and Ta5 ⁺ to the total content of Nb5 ⁺ , Ti4+, ^W6 +, ^{Bi3 +} , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ is preferably 0.25, and more preferably 0.30, 0.35, 0.37, 0.39, and 0.40 in that order. The upper limit of the cation ratio is preferably 3.10, and more preferably 2.80, 2.60, 2.40, 2.20, 2.00, 1.80, 1.60, 1.40, 1.20, 1.00, 0.80, 0.60, 0.55 in that order. It is preferable that the cation ratio is within the above range in order to increase the partial dispersion ratio PC,t in the infrared wavelength range, increase the refractive index nd, maintain high dispersion, and maintain the chemical durability of the glass. If the cation ratio is too small, the refractive index nd may decrease, and the chemical durability of the glass may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease.

The glass according to the first embodiment is preferably mainly composed of the above-mentioned glass components, i.e., Si4 ⁺ , B3 ⁺ , ^{Zr4 +} , Nb5 ⁺ , Li ⁺ , Na ⁺ , K+, Al3 ⁺ , P5 ⁺ , Cs ⁺ , ^{Mg2 +} , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , Zn2 ⁺ , La3 ⁺ , Gd3 ⁺ , Y3 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , Bi3 ⁺ , Sc3 ⁺ , Hf4 ⁺ , Lu3+, Ge4 ⁺ , and Yb3 ⁺ . The total content of the above-mentioned glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and particularly preferably 99.5% or more.

The optical glass according to the first embodiment is an oxide glass and contains O ²⁻ as an anion component. The content of O ²⁻ is preferably 90 to 100 anion %, and more preferably 95 to 100 anion %.

The optical glass according to the first embodiment may contain F 2 ⁻ as an anion component. The content of F ^{2 −} is preferably 0 to 10 anion %, and more preferably 0 to 5 anion %.

The optical glass according to the first embodiment may contain a component other than O ^2- and F ^- as an anion component. Examples of an anion component other than ^{O 2-} and F ^- include Cl ^- , Br ^- , and I ^- . However, Cl ^- , Br ^- , and I ^- are all likely to volatilize during melting of the glass. The volatilization of these components causes problems such as fluctuations in glass properties, reduction in glass homogeneity, and significant wear of melting equipment. Therefore, the content of Cl ^- is preferably less than 5 anion%, more preferably less than 3 anion%, even more preferably less than 1 anion%, particularly preferably less than 0.5 anion%, and even more preferably less than 0.25 anion%. In addition, the total content of Br ^- and I ^- is preferably less than 5 anion%, more preferably less than 3 anion%, even more preferably less than 1 anion%, particularly preferably less than 0.5 anion%, even more preferably less than 0.1 anion%, and even more preferably 0 anion%.

In the optical glass according to the first embodiment, the upper limit of the total content of F- ^{, Cl-} , ^Br- , and ^I- [ ^F- + ^Cl- + ^Br- + ^I- ] is preferably 5 anion%, and more preferably 3 anion%, 1 anion%, 0.5 anion%, and 0.1 anion% in that order. The lower limit of the total content is 0 anion%. The total content may be 0 anion%. The volatilization of these components causes problems such as fluctuations in glass properties, deterioration of glass homogeneity, and significant wear of melting equipment. Therefore, it is preferable that the total content is within the above range.

The glass according to the first embodiment is preferably basically composed of the above glass components, but may contain other components as long as they do not impede the effects of the present invention. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

In addition to the above components, the optical glass may contain a small amount of Sb3 ⁺ as a clarifier. The total amount of the clarifier (exclusive addition amount) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.9% or less, 0% or more and 0.8% or less, 0% or more and 0.7% or less, 0% or more and 0.6% or less, 0% or more and 0.5% or less, 0% or more and 0.4% or less, 0% or more and 0.3% or less, 0% or more and 0.2% or less, 0% or more and 0.1% or less, 0% or more and 0.05% or less, or 0% or more and 0.03% or less.

The total amount added is the amount of clarifier added expressed as a molar percentage when the total content of all cationic components excluding the clarifier is taken as 100%.

The optical glass also provides high transmittance over a wide range of the visible light region. To make the most of this feature, it is preferable that the glass does not contain any coloring elements. Examples of coloring elements include Co, Ni, Fe, Cr, Eu, Nd, Er, and V. Each element is preferably contained at less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, and even more preferably 0 to 50 ppm by mass, and it is particularly preferable that the glass is substantially free of these elements.

Ga, Te, Tb, etc. are components that do not need to be incorporated and are expensive components, so the ranges of the contents of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ expressed in mass % are each preferably 0 to 0.1%, more preferably 0 to 0.05%, even more preferably 0 to 0.01%, even more preferably 0 to 0.005%, even more preferably 0 to 0.001%, and particularly preferably not substantially contained.

(Glass properties)
<Abbe number νd>
In the optical glass according to the first embodiment, the Abbe number νd is preferably 30-60, and can also be 32-50, 34-45, 36-40, or 37-39.

The Abbe number vd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that relatively lower the Abbe number vd, i.e., high dispersion components, include Nb5 ⁺ , Ti4 ⁺ , Zr4 ⁺ , W6 ⁺ , Bi3 ⁺ , Ta5 ⁺ , etc. On the other hand, components that relatively increase the Abbe number vd, i.e., low dispersion components, include Si4 ⁺ , B3 ⁺ , Li ⁺ , Na ⁺ , K ⁺ , La3 ⁺ , Ba2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , etc.

In the present invention, the Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F described later are calculated as follows. That is, the refractive index at the 12 wavelengths shown in Table A is measured according to the Japanese Industrial Standards (JIS) B 7071-1 Method for measuring the refractive index of optical glass - Part 1: Minimum deviation method. Next, the refractive index of each line obtained by measurement is applied to the shot dispersion formula defined in Annex B of JIS B 7071-1 Method for measuring the refractive index of optical glass - Part 1: Minimum deviation method, and the constants of the shot dispersion formula are obtained by the least squares method. Then, the Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F described later are calculated from the values of each linear refractive index obtained using the shot dispersion formula with the constants determined.

ショットの分散式： ｎ²＝ａ₀＋ａ₁λ²＋ａ₂λ^-2＋ａ₃λ^-4＋ａ₄λ^-6＋ａ₅λ^-8
ここで、ｎは屈折率、λは波長（μｍ）、ａ₀、ａ₁、ａ₂、ａ₃、ａ₄、ａ₅は定数である。
アッベ数νｄは、ｄ線、Ｆ線、Ｃ線における各屈折率ｎｄ、ｎＦ、ｎＣを用いて次のように表される。
νｄ＝（ｎｄ－１）／（ｎＦ－ｎＣ）

Shot distribution formula: ⁿ² = _a0 + _a1 ^λ2 + _a2 λ ^-2 + _a3 λ ^-4 + _a4 λ ^-6 + _a5 λ ^-8
Here, n is the refractive index, λ is the wavelength (μm), and a ₀ , a ₁ , a ₂ , a ₃ , a ₄ , and a ₅ are constants.
The Abbe number νd is expressed as follows using the refractive indices nd, nF, and nC at the d line, F line, and C line, respectively.
νd=(nd-1)/(nF-nC)

<Refractive index nd>
In the optical glass according to the first embodiment, the refractive index nd is preferably 1.50 to 1.80, and can also be 1.60 to 1.70, 1.63 to 1.69, or 1.66 to 1.68.

The refractive index nd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that act to relatively increase the refractive index nd (high refractive index components) include Nb5 ⁺ , Ti4 ⁺ , Zr4 ⁺ , Ta5 ⁺ , La3 ⁺ , etc. On the other hand, components that act to relatively decrease the refractive index nd (low refractive index components) include Si4 ⁺ , B3 ⁺ , Li ⁺ , Na ⁺ , K ^+, etc.

<Partial dispersion ratio Pg,F>
In the optical glass according to the first embodiment, the upper limit of the partial dispersion ratio Pg,F in the visible short wavelength region is preferably 0.5900, and more preferably 0.5850, 0.5820, 0.5780, 0.5770, 0.5760, and 0.5750 in that order. By making the partial dispersion ratio Pg,F within the above range, an optical glass suitable for correcting high-order chromatic aberration can be obtained. On the other hand, the lower limit of the partial dispersion ratio Pg,F is not particularly limited, but is usually 0.5600, and preferably 0.5650.

In the optical glass according to the first embodiment, it is preferable that the partial dispersion ratio Pg,F satisfies the following formula [1-1].
Pg, F≦0.6463-0.001802×νd… [1-1]
It is more preferable that the partial dispersion ratio Pg,F satisfies the following formula [1-2], and more preferably satisfies the following formula [1-3], the following formula [1-4], the following formula [1-5], and the following formula [1-6] in that order.
Pg, F≦0.6458-0.001802×νd… [1-2]
Pg, F≦0.6453-0.001802×νd…[1-3]
Pg, F≦0.6448-0.001802×νd…[1-4]
Pg, F≦0.6446-0.001802×νd…[1-5]
Pg, F≦0.6443-0.001802×νd…[1-6]

In the optical element made of the optical glass according to the first embodiment, from the viewpoint of effectively correcting chromatic aberration over a wide wavelength range, it is preferable that the partial dispersion ratio Pg,F satisfy the above formula.

In the optical glass according to the first embodiment, the upper limit of ΔPg,F is preferably -0.0020, and more preferably -0.0025, -0.0030, -0.0035, -0.0037, and -0.0040 in that order. On the other hand, the lower limit of ΔPg,F is not particularly limited, but is usually -0.0100, and preferably -0.0080. By setting ΔPg,F in the above range, an optical glass suitable for correcting high-order chromatic aberration can be obtained.

The partial dispersion ratio Pg,F is calculated using the above shot dispersion formula.
In the present invention, the partial dispersion ratio Pg,F is calculated by using the refractive index values measured at 12 different wavelengths (spectral lines) shown in Table A above, fitting the coefficients of the wavelength term of the equation that relates the refractive index to the wavelength, called the dispersion equation of the shot, and after determining these coefficients, using the dispersion equation. By using the refractive index values measured at 12 different wavelengths, the partial dispersion ratio Pg,F can be calculated with high accuracy. On the other hand, the partial dispersion ratio Pg,F can be calculated by a simplified method by reducing the number of wavelengths at which the refractive index is measured, but the accuracy is not sufficient, and the partial dispersion ratio Pg,F calculated by the simplified method tends to be smaller than the value calculated using the refractive index measured at 12 different wavelengths. In other words, even if the partial dispersion ratio Pg,F is the same, the performance regarding the correction of actual chromatic aberration may be superior or inferior depending on the calculation method. Specifically, since the partial dispersion ratio Pg,F calculated by the simplified method as described above is estimated to be small, even if the value of Pg,F is the same as the partial dispersion ratio Pg,F calculated using refractive indices measured at 12 different wavelengths, the performance with respect to actual chromatic aberration correction may be inferior.

The partial dispersion ratio Pg,F is expressed as follows using the refractive indices ng, nF, and nC for the g-line, F-line, and C-line, respectively.
Pg,F=(ng-nF)/(nF-nC)
In addition, in a plane in which the horizontal axis represents the Abbe number vd and the vertical axis represents the partial dispersion ratio Pg,F, the normal line is expressed by the following formula.
Pg,F(0)=0.6483-(0.001802×νd)
Furthermore, the deviation ΔPg,F of the partial dispersion ratio Pg,F from the normal line is expressed as follows:
ΔPg, F=Pg, F-Pg, F(0)

<Partial dispersion ratio PC,t>
In the optical glass according to the first embodiment, the lower limit of the partial dispersion ratio PC,t in the infrared wavelength region is preferably 0.7200, and more preferably 0.7300, 0.7400, 0.7450, 0.7500, 0.7550, 0.7560, 0.7570, 0.7580, 0.7590, and 0.7600 in that order. By making the partial dispersion ratio PC,t within the above range, an optical glass suitable for high-order chromatic aberration correction can be obtained. On the other hand, the upper limit of the partial dispersion ratio PC,t is not particularly limited, but is usually 0.8500, preferably 0.8400, and more preferably 0.8300, 0.8200, 0.8100, and 0.8000 in that order.

In the optical glass according to the first embodiment, the lower limit of ΔPC,t is preferably 0.0200, and more preferably 0.0250, 0.0270, 0.0290, 0.0310, 0.0330, 0.0350, and 0.0370, in that order. On the other hand, the upper limit of ΔPC,t is not particularly limited, but is usually 0.0900, and preferably 0.0800. By setting ΔPC,t in the above range, an optical glass suitable for correcting high-order chromatic aberration can be obtained.

The partial dispersion ratio PC,t is calculated using the above shot dispersion formula.
The partial dispersion ratio P C,t is expressed as follows using the refractive indices nt, nF, and nC at the t-line, F-line, and C-line, respectively:
PC, t=(nC-nt)/(nF-nC)
Moreover, in a plane in which the horizontal axis represents the Abbe number vd and the vertical axis represents the partial dispersion ratio PC,t, the normal line is expressed by the following equation.
PC, t(0)=0.5461-(0.004667×νd)
Furthermore, the deviation ΔPC,t of the partial dispersion ratio PC,t from the normal line is expressed as follows:
ΔPC, t=PC, t-PC, t(0)

The partial dispersion ratio PC,t can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components that act to relatively increase the partial dispersion ratio PC,t include Si4 ⁺ , B3 ⁺ , ^Al3+ , Li ⁺ , etc. On the other hand, components that act to relatively decrease the partial dispersion ratio PC,t include Sr2 ⁺ , Ba2 ⁺ , Zn2 ⁺ , La3 ⁺ , Ti4 ⁺ , Nb5 ⁺ , W6 ⁺ , etc.

<ΔPg,F and ΔPC,t>
In the optical glass according to the first embodiment, ΔPg,F and ΔPc,t preferably satisfy the following (i) or (ii).
(i) When ΔPg,F is greater than −0.0037, ΔPc,t ≧ 2.875 × ΔPg,F + 0.031.
(ii) When ΔPg,F is equal to or less than −0.0037, ΔPc,t ≧ 4.750 × ΔPg,F + 0.038.

(i) In the optical glass according to the first embodiment, when ΔPg,F is greater than −0.0037, it is preferable that the following formula (A1) is satisfied, and it is more preferable that the following formulas (A2), (A3), (A4), and (A5) are satisfied in this order:
ΔPC,t≧2.875×ΔPg,F+0.031…(A1)
ΔPC,t≧2.875×ΔPg,F+0.035…(A2)
ΔPC,t≧2.875×ΔPg,F+0.037…(A3)
ΔPC,t≧2.875×ΔPg,F+0.039…(A4)
ΔPC,t≧2.875×ΔPg,F+0.041…(A5)

(ii) In the optical glass according to the first embodiment, when ΔPg,F is −0.0037 or less, it is preferable that the following formula (B1) is satisfied, and it is more preferable that the following formulas (B2), (B3), (B4), and (B5) are satisfied in this order:
ΔPC,t≧4.750×ΔPg,F+0.038…(B1)
ΔPC,t≧4.750×ΔPg,F+0.042…(B2)
ΔPC,t≧4.750×ΔPg,F+0.044…(B3)
ΔPC,t≧4.750×ΔPg,F+0.046…(B4)
ΔPC,t≧4.750×ΔPg,F+0.048…(B5)

<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 4.00 or less, more preferably 3.50 or less, 3.10 or less, 3.05 or less, 3.00 or less, 2.95 or less, 2.90 or less, 2.85 or less, and further more preferably 2.80 or less, in that order.
Components that relatively increase the specific gravity are Ba2 ⁺ , La3 ⁺ , Zr4 ⁺ , Nb5 ⁺ , Ta5 ⁺ , etc. On the other hand, components that relatively decrease the specific gravity are Si4 ⁺ , B3 ⁺ , Li ⁺ , Na ⁺ , K ⁺ , etc. The specific gravity can be controlled by appropriately adjusting the contents of these components.

<Liquid phase temperature LT>
The upper limit of the liquidus temperature LT of the optical glass according to the first embodiment is preferably 1300°C, and more preferably 1270°C, 1240°C, 1210°C, 1180°C, 1150°C, and 1100°C in that order. By setting the liquidus temperature within the above range, the melting and forming temperatures of the glass can be lowered, and as a result, the corrosion of the glass melting equipment (e.g., crucible, molten glass stirring equipment, etc.) in the melting process and the occurrence of striae due to the volatilization of the glass components themselves can be reduced. The lower limit of the liquidus temperature LT is not particularly limited, but is usually 1000°C, and preferably 1050°C. The liquidus temperature LT is determined by the balance of the contents of all the glass components. Among them, the contents of Si4 ⁺ , B3 ⁺ , Li ⁺ , Na ⁺ , K ^+, etc. have a large effect on the liquidus temperature LT. Furthermore, if the content of Zr ⁴⁺ , Al ³⁺ , etc. is large, the liquidus temperature increases.

The liquidus temperature is determined as follows: 10 cc (10 ml) of glass is placed in a platinum crucible and melted at 1250°C to 1400°C for 15 to 30 minutes, then cooled to below the glass transition temperature Tg. The glass, together with the platinum crucible, is placed in a melting furnace at the specified temperature and held there for 2 hours. The holding temperature is 1000°C or higher in 5°C or 10°C increments, and after holding for 2 hours, it is cooled and the presence or absence of crystals inside the glass is observed under a 100x optical microscope. This operation is repeated for each temperature, and the lowest temperature at which no crystals precipitate is taken as the liquidus temperature.

<Glass transition temperature Tg>
The lower limit of the glass transition temperature Tg of the optical glass according to the first embodiment is preferably 400° C., and more preferably 450° C., 470° C., and 480° C. in that order. The upper limit of the glass transition temperature Tg is preferably 600° C., and more preferably 580° C., 560° C., 550° C., 540° C., 530° C., 520° C., and 510° C. in that order.
Components that relatively lower the glass transition temperature Tg are Li ⁺ , Na ⁺ , K ⁺ , etc. Components that relatively raise the glass transition temperature Tg are La3 ⁺ , Zr4 ⁺ , Nb5 ⁺ , etc. The glass transition temperature Tg can be controlled by appropriately adjusting the contents of these components.

<Light transmittance of glass>
The light transmittance of the optical glass according to the first embodiment can be evaluated by the coloring degrees λ80 and λ5.
The spectral transmittance of a glass sample having a thickness of 10.0 mm±0.1 mm is measured in the wavelength range of 200 to 700 nm. The wavelength at which the external transmittance is 80% is defined as λ80, and the wavelength at which the external transmittance is 5% is defined as λ5.

The λ80 of the optical glass according to the first embodiment is preferably 450 nm or less, more preferably 430 nm or less, and even more preferably 410 nm or less. λ5 is preferably 400 nm or less, more preferably 380 nm or less, and even more preferably 360 nm or less.

<Chemical durability Water resistance Dw>
In the optical glass according to the first embodiment, the water resistance Dw is preferably class 5 or higher, more preferably class 4 or higher, and further preferably class 3 or higher.

Water resistance Dw is evaluated by placing a powdered glass (particle size 425 to 600 μm) of a mass equivalent to the specific gravity in a platinum cage, immersing it in a quartz glass round-bottom flask containing 80 mL of pure water (pH = 6.5 to 7.5), treating it in a boiling water bath for 60 minutes, and classifying and evaluating the grade in Table B according to the rate of weight loss (%).

<Chemical durability Acid resistance Da>
In the optical glass according to the first embodiment, the acid resistance Da is preferably class 5 or higher, more preferably class 4 or higher, and further preferably class 3 or higher.

The acid resistance Da is evaluated by placing a powdered glass (particle size 425 to 600 μm) of a mass equivalent to the specific gravity in a platinum cage, immersing it in a quartz glass round-bottom flask containing 80 mL of 0.01 mol/L nitric acid aqueous solution for 60 minutes, and classifying and evaluating the grade in Table C according to the weight loss rate (%).

<Chemical durability Latent scratch resistance D _NaOH >
In the optical glass according to the first embodiment, the latent scratch resistance D _NaOH is preferably grade 4 or higher, more preferably grade 3 or higher, and further preferably grade 2 or higher.

Latent scratch resistance D _NaOH is evaluated by classifying into classes in Table D according to the mass loss per unit area [mg/(cm2·15h)] when a glass sample with a diameter of 43.7 mm (30 ^cm2 on both sides) and a thickness of approximately 5 mm, polished on both sides, is immersed in a well-stirred 0.01 mol/L aqueous NaOH solution at ^50°C for 15 hours.

<Chemical durability Latent scratch resistance D _STPP >
In the optical glass according to the first embodiment, the latent scratch resistance D _STPP is preferably grade 4 or higher, more preferably grade 3 or higher, and further preferably grade 2 or higher.

Latent scratch resistance D _STPP is evaluated by classifying into the classes in Table E the mass loss per unit area [mg/(cm2·h) _] when a glass sample with a diameter of 43.7 mm ( ₃₀ ^cm2 on both sides) and a thickness of approximately 5 mm, polished on both sides, is immersed for one hour in a well-stirred aqueous solution of 0.01 mol/L _Na5P3O10 (STPP) at ⁵⁰ °C.

<Chemical durability Chemical durability D ₀ >
In the optical glass according to the first embodiment, the chemical durability D ₀ is preferably grade 4 or higher, more preferably grade 3 or higher, and further preferably grade 2 or higher.

Chemical durability _D0 is evaluated by classifying into classes in Table F the mass loss per unit area [10-3 mg/(cm2·h)] when a glass sample with a diameter of 43.7 mm (30 ^cm2 on both sides) and a thickness of approximately 5 mm, polished on both sides, is immersed in well-stirred pure water maintained at 50°C and pH = 7.0 ^± 0.2 and circulated through an ion exchange resin layer at a rate of ¹ L per minute.

(Optical glass manufacturing)
The glass according to the first embodiment may be produced by blending glass raw materials to obtain the above-mentioned predetermined composition, and using the blended glass raw materials in accordance with a known glass manufacturing method. For example, a plurality of compounds may be blended and thoroughly mixed to obtain a batch raw material, and the batch raw material may be placed in a quartz crucible or a platinum crucible to be roughly melted (rough melt). The molten material obtained by the rough melting is quenched and crushed to produce cullet. The cullet is then placed in a platinum crucible, heated and remelted (remelt) to obtain a molten glass, which is then clarified and homogenized, molded, and slowly cooled to obtain an optical glass. A known method may be applied to the molding and slow cooling of the molten glass.

The compounds used to prepare the batch raw materials are not particularly limited as long as the desired glass components can be introduced into the glass in the desired content, but examples of such compounds include oxides, carbonates, nitrates, hydroxides, fluorides, etc.

(Manufacturing of optical elements, etc.)
To manufacture an optical element using the optical glass according to the first embodiment, a known method may be applied. For example, in the manufacture of the optical glass, molten glass is poured into a mold and molded into a plate shape to manufacture a glass material made of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to manufacture cut pieces having a size and shape suitable for press molding. The cut pieces are heated and softened, and press molded (reheat pressed) by a known method to manufacture an optical element blank that is similar to the shape of the optical element. The optical element blank is annealed, and then ground and polished by a known method to manufacture an optical element.

The optically functional surfaces of the fabricated optical elements may be coated with anti-reflection films, total reflection films, etc., depending on the intended use.

According to one aspect of the present invention, an optical element made of the optical glass can be provided. Examples of the type of optical element include lenses such as spherical lenses and aspherical lenses, prisms, and diffraction gratings. Examples of the lens shape include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses. The optical element can be manufactured by a method including a process of processing a glass molded body made of the optical glass. Examples of the processing include cutting, milling, rough grinding, fine grinding, and polishing. When such processing is performed, the use of the glass can reduce breakage and enable a stable supply of high-quality optical elements.

Second embodiment The oxide optical glass according to the second embodiment is
the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [ ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ ] is 6.5% or more;
the cation ratio [B3 ⁺ /( ^Si4 ++B3 ⁺ )] of the content of B3 ⁺ to the total content of Si4 ⁺ and B3 ⁺ is 0.41 or more and less than 1;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
Contains substantially no Pb or As,
One or more of the following (I) to (IV) are satisfied.
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

In the optical glass according to the second embodiment, the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , ^W6+ , and ^Bi3+ [ ^Nb5 + + ^Ti4 + + ^Ta5+ + ^W6+ + Bi3 ⁺ ] is 6.5% or more. The lower limit of the total content is preferably 7%, 7.5%, 8%, and 8.5%, in that order. The upper limit of the total content is preferably 30%, and more preferably 20%, 15%, 12%, 11.5%, 11%, 10.5%, and 10%, in that order. By keeping the total content within the above range, a high refractive index and a desired Abbe number vd can be maintained.

In the optical glass according to the second embodiment, the cationic ratio [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ is 0.41 or more and less than 1. The lower limit of the cationic ratio is preferably 0.46, and more preferably 0.50, 0.51, 0.53, 0.55, 0.57, and 0.59 in this order. The upper limit of the cationic ratio is preferably 0.90, and more preferably 0.85, 0.80, 0.75, 0.70, and 0.65 in this order. By setting the cationic ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased. If the cationic ratio is too small, the partial dispersion ratio PC,t may decrease. If the cationic ratio is too large, the chemical durability of the glass may decrease.

In the optical glass according to the second embodiment, the cation ratio [(Li ⁺ + Na ⁺ + K ⁺ )/(Li ⁺ + Na ⁺ + K ⁺ + Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ is 0.55 or more. The lower limit of the cation ratio is preferably 0.75, and more preferably 0.80, 0.85, and 0.90 in that order. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.98, 0.96, and 0.94 in that order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased, the meltability of the glass can be improved, and the viscosity of the molten glass can be reduced to improve the moldability. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the second embodiment, the cation ratio [Zr4 ⁺ /(Nb5 ⁺⁺ Ti4 ^{++ Ta5++ W6} ++Bi3 ⁺ )] of the content of Zr4 ⁺ to the total content of Nb5+, ^Ti4+ , ^{Ta5 +} , W6+, and ^{Bi3 +} is 0.4 or more. The lower limit of the cation ratio is preferably 0.42, and more preferably 0.44, 0.46, 0.48, and 0.50 in this order. The upper limit of the cation ratio is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.65, 0.6, and 0.55 in this order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased and high dispersion can be maintained.

In the optical glass according to the second embodiment, the cation ratio [(Si4 ^{++ B3} ++Li ⁺⁺ Na ⁺⁺ K+ ^{Zr4 +} )/( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺⁾ ] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of Nb5+, ^Ti4 +, ^Ta5 +, ^{W6 +} , and Bi3 ⁺ is 8.6 or more. The lower limit of the cation ratio is preferably 8.8, and more preferably 9.0, 9.2, 9.4, 9.6, and 9.8 in this order. The upper limit of the cation ratio is preferably 20, and more preferably 18, 16, 14, 13, 12, and 11 in this order. By setting the cation ratio within the above range, the partial dispersion ratio PC,t in the infrared wavelength region can be increased, and the Abbe number can be adjusted.

The optical glass according to the second embodiment does not substantially contain Pb and As, which are components that are of concern for their environmental impact. That is, the content of each of Pb ions and As ions is 0%. Similarly to Pb and As, Th is also a component that is of concern for its environmental impact. Therefore, the content of Th ions is preferably 0 to 0.1%, and may be 0 to 0.05%, or 0 to 0.01%. The content of Th ions is preferably 0%. That is, it is preferable that Th is not substantially contained. Note that the Pb ions include Pb ions with different valences in addition to Pb ²⁺ . The As ions and Th ions also include ions with different valences.

The optical glass according to the second embodiment satisfies one or more of the following (I) to (IV).
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) the cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si4 ⁺ and B3 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/( ^Si4 ++B3 ⁺ )] is 0.97 or less;
The cation ratio of the total content of Li ⁺ , Na ⁺ , Mg2 ⁺ , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ^{++ Mg2} ++Ca2 ⁺ )/(Li ⁺⁺ Na ^{++ K} ++ ^{Mg2++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.75 or more.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) the cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ⁺ +Na ^{+ +K + +} Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
The cation ratio of the total content of B ³⁺ and Li ⁺ to the total content of Si ⁴⁺ , Na ⁺ and K ⁺ [(B ³⁺ + Li ⁺ )/(Si ⁴⁺ + Na ⁺ + K ⁺ )] is 0.31 or more.

That is, in the optical glass according to the second embodiment, in the case of (I) above, the cation ratio [( ^{Li +} Na ⁺ K ⁺ )/(Si ⁴⁺ + B ³⁺ )] of the total content of Li ⁺ , Na + , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.85 or less. In the case of (I) above, the upper limit of the cation ratio can be 0.80, 0.75, 0.70, 0.65, 0.60, or 0.55. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the optical glass according to the second embodiment, in the case of (II) above, the cation ratio [(Li ⁺ Na ^{+ K + )} /(Si ⁴⁺ + B ³⁺ )] of the total content of Li ⁺ , Na + , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.97 or less. In the case of (II) above, the upper limit of the cation ratio can be 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, or 0.55. The lower limit of the cation ratio is preferably 0.10, and more preferably 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength range and improving chemical durability, it is preferable that the cation ratio is within the above range.

In the optical glass according to the second embodiment, in the case of (II) above, the cation ratio [(Li ⁺ Na ^{+ Mg2} ++Ca2 ⁺ )/(Li ⁺ Na ⁺ K ^{+ Mg2} ++ ^Ca2 ++ ^Sr2 ++Ba2++Zn2+)] of the total content of Li ^+, Na ^{+, Mg2+} , and Ca2 ⁺ to the total content of Li ⁺ , Na ⁺ , K+, ^{Mg2 +} , Ca2 ⁺ , Sr2 ⁺ , ^{Ba2 +} , and ^{Zn2 +} can be 0.75 or more. In the case of (II) above, the lower limit of the cation ratio can be 0.77, 0.79, 0.81, 0.83, 0.85, 0.87, or 0.89. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.99, 0.98, and 0.95 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve formability, it is preferable that the cation ratio be in the above range.

In the optical glass according to the second embodiment, in the case of (III), the cation ratio [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ can be 0.46 or more. In the case of (III), the lower limit of the cation ratio can be 0.50, 0.51, 0.53, 0.55, 0.57, or 0.59. The cation ratio is preferably less than 1, and the upper limit is more preferably 0.90, 0.85, 0.80, 0.75, 0.70, and 0.65 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable to set the cation ratio within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the chemical durability of the glass may decrease.

In the optical glass according to the second embodiment, in the case of (IV) above, the cation ratio [(Li ⁺ Na ⁺ K ⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr ^{2+ + Ba 2+ +} Zn ²⁺ )] of the total content of Li ⁺ , Na ^{+ ,} and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ can be 0.75 or more. In the case of (IV) above, the lower limit of the cation ratio can be 0.80, 0.85, or 0.90. The upper limit of the cation ratio is preferably 1.00, and more preferably 0.98, 0.96, and 0.94 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the moldability, it is preferable that the cation ratio is within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. If the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the second embodiment, in the case of (IV) above, the cation ratio [(B3 ⁺ + Li ⁺ )/(Si4 ⁺ + Na ⁺ + K ⁺ )] of the total content of B3 ⁺ and Li ⁺ to the total content of Si4 ⁺ , Na ⁺ , and K ⁺ can be 0.31 or more. The lower limit of the cation ratio can be 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, or 1.20. The upper limit of the cation ratio is preferably 10, and more preferably 9, 8, 7, 6, 5, 4, 3, 2, and 1.8 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region, it is preferable that the cation ratio is within the above range.

In the optical glass according to the second embodiment, the partial dispersion ratio PC,t preferably satisfies the following formula [2-1].
PC, t≧0.5661+0.004667×νd…[2-1]
It is more preferable that the partial dispersion ratio PC,t satisfies the following formula [2-3], and more preferably satisfies the following formula [2-3], the following formula [2-4], the following formula [2-5], the following formula [2-6], the following formula [2-7], and the following formula [2-8] in that order.
PC, t≧0.5711+0.004667×νd…[2-2]
PC, t≧0.5731+0.004667×νd…[2-3]
PC, t≧0.5751+0.004667×νd…[2-4]
PC, t≧0.5771+0.004667×νd…[2-5]
PC, t≧0.5791+0.004667×νd… [2-6]
PC, t≧0.5811+0.004667×νd…[2-7]
PC, t≧0.5831+0.004667×νd…[2-8]

In the optical element made of the optical glass according to the second embodiment, from the viewpoint of effectively correcting chromatic aberration over a wide wavelength range, it is preferable that the partial dispersion ratio PC,t satisfies the above formula.

In the optical glass according to the second embodiment, the contents and ratios of glass components other than those mentioned above can be the same as those in the first embodiment.

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

Furthermore, the manufacture of the optical glass and the optical elements according to the second embodiment can be similar to that of the first embodiment.

The oxide optical glass according to the third embodiment is
As a glass component,
Contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ ;
Contains one or more selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ ;
ΔPg,F and ΔPC,t satisfy the following (i) or (ii).
(i) When ΔPg,F is greater than −0.0037, ΔPc,t ≧ 2.875 × ΔPg,F + 0.031.
(ii) When ΔPg,F is equal to or less than −0.0037, ΔPc,t ≧ 4.750 × ΔPg,F + 0.038.

The optical glass according to the third embodiment contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ as glass components.

The optical glass according to the third embodiment contains, as a glass component, one or more elements selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ . The optical glass according to the second embodiment preferably contains Li ⁺ and Na ⁺ .

In the optical glass according to the third embodiment, ΔPg,F and ΔPc,t satisfy the following (i) or (ii).
(i) When ΔPg,F is greater than −0.0037, ΔPc,t ≧ 2.875 × ΔPg,F + 0.031.
(ii) When ΔPg,F is equal to or less than −0.0037, ΔPc,t ≧ 4.750 × ΔPg,F + 0.038.

(i) In the optical glass according to the first embodiment, when ΔPg,F is greater than −0.0037, it is preferable that the following formula (A1) is satisfied, and it is more preferable that the following formulas (A2), (A3), (A4), and (A5) are satisfied in this order:
ΔPC,t≧2.875×ΔPg,F+0.031…(A1)
ΔPC,t≧2.875×ΔPg,F+0.035…(A2)
ΔPC,t≧2.875×ΔPg,F+0.037…(A3)
ΔPC,t≧2.875×ΔPg,F+0.039…(A4)
ΔPC,t≧2.875×ΔPg,F+0.041…(A5)

(ii) In the optical glass according to the first embodiment, when ΔPg,F is −0.0037 or less, it is preferable that the following formula (B1) is satisfied, and it is more preferable that the following formulas (B2), (B3), (B4), and (B5) are satisfied in this order:
ΔPC,t≧4.750×ΔPg,F+0.038…(B1)
ΔPC,t≧4.750×ΔPg,F+0.042…(B2)
ΔPC,t≧4.750×ΔPg,F+0.044…(B3)
ΔPC,t≧4.750×ΔPg,F+0.046…(B4)
ΔPC,t≧4.750×ΔPg,F+0.048…(B5)

In the optical glass according to the third embodiment, the lower limit of the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [ ^Nb5 + + ^Ti4 + + Ta5 ⁺ + ^W6 + + Bi3 ⁺ ] is preferably 6.5%, more preferably 7%, 7.5%, 8%, and 8.5% in that order. The upper limit of the total content is preferably 30%, more preferably 20%, 15%, 12%, 11.5%, 11%, 10.5%, and 10% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number vd, it is preferable that the total content be within the above range.

In the optical glass according to the third embodiment, the lower limit of the cation ratio [(Li ⁺ Na ⁺ K ⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is preferably 0.55, more preferably 0.75, 0.80, 0.85, and 0.90 in that order. The upper limit of the cation ratio is preferably 1.00, more preferably 0.98, 0.96, and 0.94 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the moldability, it is preferable that the cation ratio is within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. On the other hand, if the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the third embodiment, the lower limit of the cation ratio [Zr4 ⁺ /(Nb5 ^{++ Ti4} ++Ta5 ^{++ W6++} Bi3 ⁺ )] of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5+, ^{W6 +} , and ^Bi3+ is preferably 0.4, more preferably 0.42, 0.44, 0.46, 0.48, and 0.50 in this order. The upper limit of the cation ratio is preferably 1, more preferably 0.9, 0.8, 0.7, 0.65, 0.6, and 0.55 in this order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region and maintaining high dispersion, it is preferable that the cation ratio is within the above range.

In the optical glass according to the third embodiment, the lower limit of the cation ratio [(Si4 ^{+ B3} ++Li ⁺ Na ⁺ K ⁺ Zr4 ⁺ )/( ^Nb5 ++Ti4 ^{+ Ta5} + ^W6 +Bi3+ ⁾ ] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K+, and Zr4 ⁺ to the total content of Nb5+, ^Ti4 +, ^{Ta5 +} , ^W6+ , and ^{Bi3 +} is preferably 8.6, more preferably 8.8, 9.0, 9.2, 9.4, 9.6, and 9.8 in that order. The upper limit of the cation ratio is preferably 20, more preferably 18, 16, 14, 13, 12, and 11 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region and adjusting the Abbe number, it is preferable that the cation ratio is within the above range.

The optical glass according to the third embodiment is preferably substantially free of Pb and As, which are components of concern for their environmental impact. That is, the respective contents of Pb ions and As ions are preferably 0%. Furthermore, Th is also a component of concern for its environmental impact, similar to Pb and As. Therefore, the content of Th ions is preferably 0-0.1%, and may be 0-0.05%, or 0-0.01%. The content of Th ions is preferably 0%. That is, it is preferable that Th is not substantially included. Note that the Pb ions include Pb ions having different valences in addition to Pb ²⁺ . The As ions and Th ions also include ions having different valences.

In the optical glass according to the third embodiment, the partial dispersion ratio PC,t preferably satisfies the following formula [2-1].
PC, t≧0.5661+0.004667×νd…[2-1]
It is more preferable that the partial dispersion ratio PC,t satisfies the following formula [2-3], and more preferably satisfies the following formula [2-3], the following formula [2-4], the following formula [2-5], the following formula [2-6], the following formula [2-7], and the following formula [2-8] in that order.
PC, t≧0.5711+0.004667×νd…[2-2]
PC, t≧0.5731+0.004667×νd…[2-3]
PC, t≧0.5751+0.004667×νd…[2-4]
PC, t≧0.5771+0.004667×νd…[2-5]
PC, t≧0.5791+0.004667×νd… [2-6]
PC, t≧0.5811+0.004667×νd…[2-7]
PC, t≧0.5831+0.004667×νd…[2-8]

In the optical element made of the optical glass according to the third embodiment, from the viewpoint of effectively correcting chromatic aberration over a wide wavelength range, it is preferable that the partial dispersion ratio PC,t satisfies the above formula.

The optical glass according to the third embodiment may satisfy one or more of the conditions (I) to (IV) detailed in the first embodiment.

In the optical glass according to the third embodiment, the contents and ratios of glass components other than those mentioned above can be the same as those in the first embodiment.

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

Furthermore, the manufacture of the optical glass and the optical elements according to the third embodiment can be similar to that of the first embodiment.

Fourth embodiment The oxide optical glass according to the fourth embodiment is
As a glass component,
Contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ ;
Contains one or more selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ ;
P C,t satisfies the following formula [2-1].
PC, t≧0.5661+0.004667×νd…[2-1]

The optical glass according to the fourth embodiment contains Si ⁴⁺ , B ³⁺ , Zr ⁴⁺ , and Nb ⁵⁺ as glass components.

The optical glass according to the fourth embodiment contains, as a glass component, one or more elements selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ . The optical glass according to the second embodiment preferably contains Li ⁺ and Na ⁺ .

In the optical glass according to the fourth embodiment, the partial dispersion ratio PC,t satisfies the following formula [2-1].
PC, t≧0.5661+0.004667×νd…[2-1]
In the optical glass according to the fourth embodiment, the partial dispersion ratio PC,t preferably satisfies the following formula [2-2], and more preferably satisfies the following formulas [2-3], [2-4], [2-5], [2-6], [2-7], and [2-8] in this order.
PC, t≧0.5711+0.004667×νd…[2-2]
PC, t≧0.5731+0.004667×νd…[2-3]
PC, t≧0.5751+0.004667×νd…[2-4]
PC, t≧0.5771+0.004667×νd…[2-5]
PC, t≧0.5791+0.004667×νd… [2-6]
PC, t≧0.5811+0.004667×νd…[2-7]
PC, t≧0.5831+0.004667×νd…[2-8]

The method for calculating the partial dispersion ratio PC,t is as described in the first embodiment. When the partial dispersion ratio PC,t satisfies the above formula, the optical element made of the optical glass according to the fourth embodiment can effectively correct chromatic aberration over a wide wavelength range.

In the optical glass according to the fourth embodiment, the partial dispersion ratio Pg,F preferably satisfies the following formula [1-1].
Pg, F≦0.6463-0.001802×νd… [1-1]
In the optical glass according to the fourth embodiment, the partial dispersion ratio Pg,F more preferably satisfies the following formula [1-2], and further more preferably satisfies the following formulas [1-3], [1-4], [1-5], and [1-6] in this order:
Pg, F≦0.6458-0.001802×νd… [1-2]
Pg, F≦0.6453-0.001802×νd…[1-3]
Pg, F≦0.6448-0.001802×νd…[1-4]
Pg, F≦0.6446-0.001802×νd…[1-5]
Pg, F≦0.6443-0.001802×νd…[1-6]

The method for calculating the partial dispersion ratios Pg and F is as described in the first embodiment. When the partial dispersion ratios Pg and F satisfy the above formula, the optical element made of the optical glass according to the fourth embodiment can effectively correct chromatic aberration over a wide wavelength range.

In the optical glass according to the fourth embodiment, the lower limit of the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [ ^Nb5 + + ^Ti4 + + Ta5 ⁺ + ^W6 + + Bi3 ⁺ ] is preferably 6.5%, more preferably 7%, 7.5%, 8%, and 8.5% in that order. The upper limit of the total content is preferably 30%, more preferably 20%, 15%, 12%, 11.5%, 11%, 10.5%, and 10% in that order. From the viewpoint of maintaining a high refractive index and a desired Abbe number vd, it is preferable that the total content be within the above range.

In the optical glass according to the fourth embodiment, the lower limit of the cation ratio [(Li ⁺ Na ⁺ K ⁺ )/(Li ⁺ Na ⁺ K ⁺ Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ^{+ ,} Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is preferably 0.55, more preferably 0.75, 0.80, 0.85, and 0.90 in that order. The upper limit of the cation ratio is preferably 1.00, more preferably 0.98, 0.96, and 0.94 in that order. From the viewpoints of increasing the partial dispersion ratio PC,t in the infrared wavelength region, improving the meltability of the glass, and further reducing the viscosity of the molten glass to improve the moldability, it is preferable that the cation ratio is within the above range. If the cation ratio is too small, the partial dispersion ratio PC,t may decrease. On the other hand, if the cation ratio is too large, the thermal stability of the glass may decrease, and the refractive index nd may decrease.

In the optical glass according to the fourth embodiment, the lower limit of the cation ratio [Zr4 ⁺ /(Nb5 ^{++ Ti4++} Ta5 ^{++ W6} ++Bi3 ⁺ )] of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5+, ^{W6 +} , and Bi3 ⁺ is preferably 0.4, more preferably 0.42, 0.44, 0.46, 0.48, and 0.50 in this order. The upper limit of the cation ratio is preferably 1, more preferably 0.9, 0.8, 0.7, 0.65, 0.6, and 0.55 in this order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region and maintaining high dispersion, it is preferable that the cation ratio is within the above range.

In the optical glass according to the fourth embodiment, the lower limit of the cation ratio [(Si4 ^{+ B3} ++Li ⁺ Na ⁺ K ⁺ Zr4 ⁺⁾ /( ^Nb5 ++Ti4 ^{+ Ta5} + ^W6 +Bi3+ ⁾ ] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K+, and Zr4 ⁺ to the total content of Nb5+, ^Ti4 +, ^{Ta5 +} , ^W6+ , and ^{Bi3 +} is preferably 8.6, more preferably 8.8, 9.0, 9.2, 9.4, 9.6, and 9.8 in that order. The upper limit of the cation ratio is preferably 20, more preferably 18, 16, 14, 13, 12, and 11 in that order. From the viewpoint of increasing the partial dispersion ratio PC,t in the infrared wavelength region and adjusting the Abbe number, it is preferable that the cation ratio is within the above range.

The optical glass according to the fourth embodiment is preferably substantially free of Pb and As, which are components of concern for their environmental impact. That is, the respective contents of Pb ions and As ions are preferably 0%. Furthermore, Th is also a component of concern for its environmental impact, similar to Pb and As. Therefore, the content of Th ions is preferably 0-0.1%, and may be 0-0.05%, or 0-0.01%. The content of Th ions is preferably 0%. That is, it is preferable that Th is not substantially included. Note that the Pb ions include Pb ions with different valences in addition to Pb ²⁺ . The As ions and Th ions also include ions with different valences.

The optical glass according to the fourth embodiment may satisfy one or more of (I) to (IV) detailed in the first embodiment.

In the optical glass according to the fourth embodiment, the contents and ratios of glass components other than those mentioned above can be the same as those in the first embodiment.

In addition, in the optical glass according to the fourth embodiment, the glass properties other than those described above can be the same as those of the first embodiment.

Furthermore, the manufacture of the optical glass and the optical elements according to the fourth embodiment can be similar to that of the first embodiment.

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
Glass samples having the glass compositions shown in Table 1 (Table 1(1), Table 1(2), Table 1(3)), Table 2 (Table 2(1), Table 2(2), Table 2(3)), Table 3 (Table 3(1), Table 3(2), Table 3(3)), Table 4 (Table 4(1), Table 4(2), Table 4(3)), Table 5 (Table 5(1), Table 5(2), Table 5(3)), Table 6 (Table 6(1), Table 6(2), Table 6(3)), Table 7 (Table 7(1), Table 7(2), Table 7(3)), Table 8 (Table 8(1), Table 8(2), Table 8(3)), Table 9 (Table 9(1), Table 9(2), Table 9(3)), and Table 10 (Table 10(1), Table 10(2), Table 10(3)) were prepared by the following procedure, and various evaluations were performed.

[Production of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to the constituent components of the glass were prepared as raw materials, and the raw materials were weighed, mixed, and thoroughly mixed so that the resulting optical glass had the glass composition shown in Tables 1 to 4. The mixed raw materials (batch raw materials) thus obtained were placed in a platinum crucible and heated at 1350°C to 1400°C for 2 to 4 hours to form molten glass, which was then stirred to homogenize and clarified, after which the molten glass was cast into a mold preheated to an appropriate temperature. The cast glass was heat-treated for 30 minutes at a temperature near the glass transition temperature Tg, and allowed to cool to room temperature in a furnace to obtain a glass sample.

[Confirmation of glass composition]
The contents of each glass component in the obtained glass samples were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and it was confirmed that each composition was as shown in Tables 1 to 4. In all glass samples, the contents of Pb ions and As ions were 0%.

[Measurement of optical properties]
The obtained glass sample was further annealed at about the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature in a furnace at a temperature drop rate of -30°C/hour to obtain an annealed sample. The refractive index, Abbe number vd, partial dispersion ratios Pg,F, ΔPg,F, partial dispersion ratios PC,t, ΔPC,t, specific gravity, glass transition temperature Tg, liquidus temperature LT, λ80, and λ5 of the obtained annealed sample were measured.

(i) Refractive indexes nd, ng, nF, nC, Abbe number νd, partial dispersion ratio Pc,t and partial dispersion ratio Pg,F
The refractive index of the annealed sample was measured at the 12 wavelengths shown in Table A according to JIS B 7071-1, Measurement of refractive index of optical glass, Part 1: Minimum deviation angle method.
Next, the refractive index of each line obtained by the measurement was applied to the Schott dispersion formula defined in JIS B 7071-1, Measurement of the refractive index of optical glass - Part 1: Minimum deviation angle method, Appendix B, and the constants of the Schott dispersion formula were obtained by the least squares method. Then, the Abbe number νd, partial dispersion ratio PC,t, and partial dispersion ratio Pg,F were calculated using the Schott dispersion formula with the determined constants.

ショットの分散式： ｎ²＝ａ₀＋ａ₁λ²＋ａ₂λ^-2＋ａ₃λ^-4＋ａ₄λ^-6＋ａ₅λ^-8
ここで、ｎは屈折率、λは波長（μｍ）、ａ₀、ａ₁、ａ₂、ａ₃、ａ₄、ａ₅は定数である。
なお、屈折ｎｄとは、波長５８７．５６ｎｍにおける屈折率である。
アッベ数νｄは、ｄ線、Ｆ線、Ｃ線における各屈折率ｎｄ、ｎＦ、ｎＣを用いて次のように表される。
νｄ＝（ｎｄ－１）／（ｎＦ－ｎＣ）
部分分散比ＰＣ，ｔは、ｔ線、Ｆ線、Ｃ線における各屈折率ｎｔ、ｎＦ、ｎＣを用いて次のように表される。
ＰＣ，ｔ＝（ｎＣ－ｎｔ）／（ｎＦ－ｎＣ）
部分分散比Ｐｇ，Ｆは、ｇ線、Ｆ線、Ｃ線における各屈折率ｎｇ、ｎＦ、ｎＣを用いて次のように表される。
Ｐｇ，Ｆ＝（ｎｇ－ｎＦ）／（ｎＦ－ｎＣ）

Shot distribution formula: ⁿ² = _a0 + _a1 ^λ2 + _a2 λ ^-2 + _a3 λ ^-4 + _a4 λ ^-6 + _a5 λ ^-8
Here, n is the refractive index, λ is the wavelength (μm), and a ₀ , a ₁ , a ₂ , a ₃ , a ₄ , and a ₅ are constants.
The refraction nd is the refractive index at a wavelength of 587.56 nm.
The Abbe number νd is expressed as follows using the refractive indices nd, nF, and nC at the d line, F line, and C line, respectively.
νd=(nd-1)/(nF-nC)
The partial dispersion ratio P C,t is expressed as follows using the refractive indices nt, nF, and nC at the t-line, F-line, and C-line, respectively:
PC, t=(nC-nt)/(nF-nC)
The partial dispersion ratio Pg,F is expressed as follows using the refractive indices ng, nF, and nC for the g-line, F-line, and C-line, respectively.
Pg,F=(ng-nF)/(nF-nC)

(ii) ΔPC,t, ΔPg,F
In a plane in which the horizontal axis represents the Abbe number vd and the vertical axis represents the partial dispersion ratio PC,t, the normal line PC,t(0) is expressed by the following equation.
PC, t(0)=0.5461-(0.004667×νd)
The deviation of the partial dispersion ratio PC,t from the normal line, ΔPC,t, was calculated based on the following formula.
ΔPC, t=PC, t-PC, t(0)
In addition, in a plane in which the horizontal axis represents the Abbe number νd and the vertical axis represents the partial dispersion ratio Pg,F, the normal line Pg,F(0) is expressed by the following equation.
Pg,F(0)=0.6483-(0.001802×νd)
The deviation Δ of the partial dispersion ratio Pg,F from the normal line, Pg,F, was calculated based on the following formula.
ΔPg, F=Pg, F-Pg, F(0)

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

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

(v) Liquidus temperature LT
The glass was placed in a furnace heated to a prescribed temperature and held there for about 2 hours. After cooling, the inside of the glass was observed under an optical microscope at 40 to 100 magnifications to measure the liquidus temperature from the presence or absence of crystals.

(vi) λ80, λ5
The annealed sample was processed to have a thickness of 10 mm and parallel optically polished flat surfaces, and the spectral transmittance was measured in the wavelength range from 280 nm to 700 nm. The intensity of the light beam perpendicularly incident on one of the optically polished flat surfaces was defined as intensity A, and the intensity of the light beam emerging from the other flat surface was defined as intensity B, and the spectral transmittance B/A was calculated. The wavelength at which the spectral transmittance was 80% was defined as λ80, and the wavelength at which the spectral transmittance was 5% was defined as λ5. The spectral transmittance also includes the reflection loss of the light beam on the sample surface.

[Chemical durability Water resistance Dw]
The obtained glass sample was made into powder glass (particle size 425-600 μm), and the powder glass of a mass equivalent to the specific gravity was placed in a platinum cage, which was then immersed in a quartz glass round-bottom flask containing 80 mL of pure water (pH = 6.5-7.5) and treated in a boiling water bath for 60 minutes. The glass samples were classified into the classes in Table B according to the weight loss rate (%) and evaluated.

[Chemical durability Acid resistance Da]
The obtained glass sample was made into powder glass (particle size 425 to 600 μm), and the powder glass of a mass corresponding to the specific gravity was placed in a platinum cage, which was then immersed in a quartz glass round-bottom flask containing 80 mL of 0.01 mol/L nitric acid aqueous solution for 60 minutes. The glass was classified into the grades in Table C according to the weight loss rate (%) and evaluated.

[Chemical durability Latent scratch resistance D _NaOH ]
The obtained glass samples were processed into specimens with a diameter of 43.7 mm (30 ^cm2 on both sides) and a thickness of about 5 mm, which were polished on both sides. These were immersed in a well-stirred 0.01 mol/L NaOH aqueous solution at 50°C for 15 hours, and the mass loss per unit area [mg/( ^cm2 ·15h)] was classified and evaluated according to the grades in Table D.

[Chemical durability Latent scratch resistance D _STPP ]
The obtained glass samples were processed into specimens with a diameter of 43.7 mm (30 ^cm2 on both sides) and a thickness of about 5 mm, which were polished on both sides. These were immersed for 1 hour in a well-stirred 50°C _0.01 mol/L _Na5P3O10 (STPP ₎ aqueous solution, and classified and evaluated into the classes shown in Table E according to the mass loss per unit area [mg/( ^cm2 ·h)].

[Chemical durability Chemical durability D ₀ ]
The obtained glass samples were processed into specimens with a diameter of 43.7 mm (30 ^cm2 on both sides) and a thickness of about 5 mm, both sides of which were polished. These were circulated through an ion exchange resin layer at a rate of 1 L per minute, and immersed in well-stirred pure water maintained at 50°C and pH = 7.0 ± 0.2. The mass loss per unit area [ ^10-3 mg/( ^cm2 ·h)] was then classified and evaluated according to the grades in Table F.

Example 2
Using each of the optical glasses produced in Example 1, lens blanks were produced by a known method, and the lens blanks were processed by a known method such as polishing to produce various lenses.
The optical lenses produced include various lenses such as a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, and a convex meniscus lens.
By combining each of the lenses with a lens made of low dispersion glass having an Abbe number of 65 or more, such as fluorophosphate glass, it was possible to satisfactorily correct high-order chromatic aberration in the infrared region.

In addition, because glass has a relatively low specific gravity, each lens is lighter than lenses with similar optical properties and size, making them suitable for use in various imaging devices, especially autofocus imaging devices, due to their energy-saving capabilities. In the same manner, prisms were made using the various optical glasses made in Example 1.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

For example, by adjusting the composition described in the specification to the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be produced.
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 (7)

The content of Si4 ⁺ is 5 to 50 cation %,
The B3 ⁺ content is 10 to 60 cation %,
The content of Nb5 ⁺ is 3 cation% or more,
the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [ ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ ] is 6.5 cation % or more;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
a cation ratio [(Li ^{+ +} Na ⁺ Mg ²⁺ +Ca ²⁺ )/(Li ^{+ +} Na + ⁺ K +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , Mg ²⁺ , and Ca ²⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
the cation ratio of the content of Nb5 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Nb5 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.5 or more;
a cation ratio of the total content of B3 ⁺ and Li ⁺ to the total content of Si4 ⁺ , Na ⁺ , and K ⁺ [(B3 ⁺ + Li ⁺ )/(Si4 ⁺ + Na ⁺ + K ⁺ )] is 0.40 or more;
Contains substantially no Pb or As,
PC,t satisfies the following formula [2-2],
PC, t≧0.5711+0.004667×νd…[2-2]
An oxide optical glass that satisfies one or more of the following (I) to (IV):
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.97 or less.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/(Li ⁺⁺ Na ⁺⁺ K ⁺⁺ Mg2++ ^Ca2 ++ ^{Sr2 ++ Ba2} ++Zn2 ⁺ )] is 0.75 or more. The content of Si4 ⁺ is 5 to 50 cation %,
The B3 ⁺ content is 10 to 60 cation %,
The content of Nb5 ⁺ is 3 cation% or more,
the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [ ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ ] is 6.5 cation % or more;
the cation ratio [B3 ⁺ /( ^Si4 ++B3 ⁺ )] of the content of B3 ⁺ to the total content of Si4 ⁺ and B3 ⁺ is 0.41 or more and less than 1;
a cation ratio [(Li ^{+ +} Na ⁺ +K ⁺ )/(Li ^{+ +} Na + +K ⁺ +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.55 or more;
the cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.4 or more;
a cation ratio [(Si4 ^{+ + B3+ +} Li ⁺ + Na ⁺ + K ⁺ + Zr4 ⁺⁾ /( ^Nb5 + + Ti4 ⁺ + Ta5 ⁺ + ^W6+ + Bi3 ⁺ )] of the total content of Si4 ⁺ , ^B3+ , Li ⁺ , Na ⁺ , K ⁺ , and Zr4 ⁺ to the total content of ^Nb5 +, ^Ti4 +, ^Ta5 +, ^W6 +, and ^Bi3 + is 8.6 or more;
a cation ratio [(Li ^{+ +} Na ⁺ Mg ²⁺ +Ca ²⁺ )/(Li ^{+ +Na + +} K +Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )] of the total content of Li ⁺ , Na ⁺ , Mg ²⁺ , and Ca ²⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ is 0.75 or more;
the cation ratio of the content of Nb5 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Nb5 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.5 or more;
a cation ratio of the total content of B3 ⁺ and Li ⁺ to the total content of Si4 ⁺ , Na ⁺ , and K ⁺ [(B3 ⁺ + Li ⁺ )/(Si4 ⁺ + Na ⁺ + K ⁺ )] is 0.40 or more;
Contains substantially no Pb or As,
An oxide optical glass that satisfies one or more of the following (I) to (IV):
(I) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(II) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.97 or less.
(III) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more.
(IV) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Li ⁺ , Na ⁺ , K ⁺ , Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ , and Zn2 ⁺ [(Li ⁺⁺ Na ⁺⁺ K ⁺ )/(Li ⁺⁺ Na ⁺⁺ K ⁺⁺ Mg2++ ^Ca2 ++ ^{Sr2 ++ Ba2} ++Zn2 ⁺ )] is 0.75 or more. 3. The oxide optical glass according to claim 1, which satisfies one or more of the following (1) to (3):
(1) The cation ratio [Na ⁺ /(Li ^{+ +} Na ⁺ +K ⁺ )] of the content of Na ⁺ to the total content of Li ⁺ , Na + and K ⁺ is 0.15 or more.
(2) The cation ratio of the total content of Li ⁺ , Na ⁺ , and K ⁺ to the total content of Si ⁴⁺ and B ³⁺ [(Li ⁺ +Na ⁺ +K ⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.85 or less.
(3) The cation ratio of the content of B ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [B ³⁺ /(Si ⁴⁺ +B ³⁺ )] is 0.46 or more. 3. The oxide optical glass according to claim 1, which satisfies one or more of the following (4) to (20):
(4) The cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ and ^Bi3+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.44 or more.
(5) The Ca2 ⁺ content is 10 cation % or less.
(6) The La3 ⁺ content is 4 cation % or less.
(7) The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ [Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ] is 10 cation % or less.
(8) The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ [Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ] is 10 cation % or less.
(9) The total content of La ³⁺ , Gd ³⁺ and Y ³⁺ [La ³⁺ +Gd ³⁺ +Y ³⁺ ] is 4 cation % or less.
(10) The total content of Nb ⁵⁺ and Zr ⁴⁺ [Nb ⁵⁺ +Zr ⁴⁺ ] is 7 cation % or more.
(11) The cation ratio of the content of Ti4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ and ^Bi3+ [Ti4 ⁺ /( ^Nb5 ++ ^Ti4 ++Ta5++ ^W6 ++ ^{Bi3 +} )] is 0.5 or less.
(12) The cation ratio of the content of Nb5 ⁺ to the total content of Nb5 ⁺ , Zr4 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3 + [Nb5 ⁺ /( ^Nb5 ++ ^Zr4 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.3 or more.
(13) The cation ratio of the content of Ti4 ⁺ to the total content of Nb5 ⁺ , Zr4 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and ^Bi3+ [Ti4 ^{+ /} ( ^Nb5 ++ ^Zr4 ++Ti4++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.3 or less.
(14) The cation ratio of the total content of Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , and Ba2 ⁺ to the total content of Si4 ⁺ and ^B3 + [(Mg2 ⁺ + Ca2 ⁺ + Sr2 ⁺ + Ba2 ⁺ )/(Si4 ⁺ + B3 ⁺ )] is 0.2 or less.
(15) The cation ratio of the total content of Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ and Zn2 ⁺ to the total content of Si4 ⁺ and ^B3+ [(Mg2 ⁺ + ^Ca2+ + Sr2 ⁺ + Ba2 ⁺ + Zn2 ⁺ )/(Si4 ⁺ + B3 ⁺ )] is 0.2 or less.
(16) The cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ to the total content of Si ⁴⁺ and B ³⁺ [(La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Si ⁴⁺ +B ³⁺ )] is 0.08 or less.
(17) The cation ratio of the total content of Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , and Ba2 ⁺ to the total content of Li ⁺ , Na ⁺ , and K ⁺ [(Mg2 ⁺ +Ca2 ⁺ +Sr2 ⁺ + ^Ba2+ )/(Li ⁺ +Na ⁺ +K ⁺ )] is 0.4 or less.
(18) The cation ratio of the total content of Mg2 ⁺ , Ca2 ⁺ , Sr2 ⁺ , Ba2 ⁺ and Zn2 ⁺ to the total content of Li ⁺ , Na ⁺ and K ⁺ [(Mg2 ⁺ + ^Ca2+ +Sr2+ + ^{Ba2 +} +Zn2 ⁺ )/(Li ⁺ +Na ⁺ +K ⁺ )] is 0.4 or less.
(19) The cation ratio of the total content of La3 ⁺ , Gd3 ⁺ , and Y3 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , and Bi3 ⁺ [( ^La3 ++ ^Gd3 ++ ^Y3+ )/( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++Bi3 ⁺ )] is 0.6 or less.
(20) The cation ratio of the content of Zr4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , Ta5 ⁺ , W6 ⁺ , ^{Bi3+, Mg2+ , Ca2 +} , Sr2+, Ba2 ⁺ , and ^Zn2+ [Zr4 ⁺ /( ^Nb5 ++ ^Ti4 ++ ^Ta5 ++ ^W6 ++ ^Bi3 ++Mg2 ^{++Ca2 ++ Sr2} ++ ^Ba2 ++Zn2 ⁺ )] is 0.17 or more. 5. The oxide optical glass according to claim 4, wherein Pg and F satisfy the following formula [1-1]:
Pg, F≦0.6463-0.001802×νd…[1-1] 6. The oxide optical glass according to claim 1, wherein the cation ratio of the total content of Nb5 ⁺ and Ti4 ⁺ to the total content of Nb5 ⁺ , Ti4 ⁺ , W6 ⁺ , and Bi3 ⁺ [( ^Nb5 + + Ti4 ⁺ )/(Nb5 ⁺ + Ti4 ⁺ + ^W6 + + Bi3 ⁺ )] is 0.5 or more. 7. An optical element comprising the oxide optical glass according to claim 1.