JP2021054709A - Optical glass and optical element - Google Patents

Abstract

To provide an optical glass that reduces the occurrence of striae during production, and is suitable for chromatic aberration correction.SOLUTION: A fluorophosphate-based optical glass has a viscosity of 10.0 dPa s or more at a liquid phase temperature, satisfies Pg, F>-0.0004νd+0.5720, has a refractive index (nd) of 1.45000 or more and 1.65000 or less, has an Abbe number (νd) of 45.0 or more and 85.0 or less, and contains in cation% the components of P5+ 5% or more and 55% or less, Al3+ 5% or more and 50% or less, and Ba2+ 3% or more and 50% or less.SELECTED DRAWING: None

Description

The present invention relates to optical glass and an optical element comprising the same.

Optical glass having anomalous dispersibility has been conventionally known, and an optical glass having a high anomalous dispersibility can be a lens suitable for correcting chromatic aberration.

Futurate-based optical glass is one of the optical glasses having high anomalous dispersibility. In fluorinated optical glass, the glass components tend to volatilize at high temperatures, and when the molten glass is poured into a mold, if the viscosity of the molten glass is low, the convection of the glass in the mold becomes remarkable, and the homogeneity of the glass composition becomes stable. It cannot be maintained and a pulse occurs. The pulse refers to a homogeneous portion of optical properties such as the refractive index, which is not preferable for optical glass materials.

In order to solve the above problem, a method of lowering the temperature of the molten glass can be considered. By lowering the temperature of the molten glass, volatilization is reduced and the viscosity of the glass is increased, so that convection of the glass can be suppressed. However, if the temperature of the glass is lowered too much, it becomes easy to devitrify the glass, which increases the difficulty of manufacturing.

For example, Patent Document 1 discloses a fluorinated optical glass having anomalous dispersibility and having a viscosity at a liquid phase temperature of 4 dPa · s or more. However, the glass of the example of Patent Document 1 does not have the desired anomalous dispersibility, although the viscosity at the liquidus temperature is improved to some extent.

Japanese Unexamined Patent Publication No. 2008-137877

An object of the present invention is to reduce the occurrence of veins during manufacturing and to provide an appropriate optical glass by correcting chromatic aberration.

As a result of diligent research, the present inventors have found an appropriate optical glass by reducing the occurrence of veins during manufacturing and correcting chromatic aberration, and have reached the present invention. That is, the present invention includes the following.
[1] A fluorinated optical glass having a viscosity at a liquid phase temperature of 10.0 dPa · s or more and satisfying Pg, F> -0.0004νd + 0.5720.
[2] The optical glass according to [1], wherein the refractive index (nd) is 1.45000 or more and 1.65000 or less, and the Abbe number (νd) is 45.0 or more and 85.0 or less.
[3] The optical glass according to [1] or [2], which contains a component in the following range in% cation;
P ⁵⁺ 5% or more, 55% or less Al ³⁺ 5% or more, 50% or less,
Ba ²⁺ 3% or more, 50% or less.
[4] The optical glass according to any one of [1] to [3], which contains 20% or less ^{of Ti 4+ in% cation.}
[5] The optical glass according to any one of [1] to [4], which contains 30% or less ^{of Nb 5+ in% cation.}
[6] An optical element made of the optical glass according to any one of [1] to [5].

The optical glass of the present invention is an optical glass that reduces the occurrence of veins during manufacturing and is suitable for chromatic aberration correction.

It is a photograph of the polished surface of the optical glass of Example 1. It is a photograph of the polished surface of the optical glass of Comparative Example 2.

Hereinafter, the present invention will be described, but the present invention is not limited to the mode for carrying out the invention.

First, the glass characteristics of the present invention and the composition of the optical glass will be described. In the present specification, the content and the total content of cationic components, unless otherwise indicated, shall be displayed by cationic% (cation%), the anionic component ^{(herein, O 2-, F -, Cl} -, Unless otherwise specified, the content of Br ⁻ and I ⁻ ) and the total content shall be indicated by anion%.
Here, the cation% is a value calculated by "(the number of cations of interest / the total number of cations of the glass component) x 100", and means the molar percentage of the amount of cations of interest with respect to the total amount of cation components.
Further, the anion% is a value calculated by "(the number of anions of interest / the total number of anions of the glass component) x 100", and means the molar percentage of the amount of anions of interest with respect to the total amount of anion components.

The ratio of the contents of the cation components to each other is equal to the ratio of the contents of the cation components of interest by the cation% display, and the ratio of the contents of the anion components to each other is the ratio of the contents of the anion components of interest by the anion% display. equal.

The content of glass constituents is quantified by known methods such as inductively coupled plasma emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and ion chromatography. In the present invention, the content of the glass component is 0%, which means that the component is substantially free of the glass component, and it is permissible that the component is contained at an unavoidable impurity level. ..

The refractive index of each wavelength is measured up to the sixth decimal place according to JIS B 7071 and is expressed in the fifth decimal place. The main variance nF-nC (in the present specification, nF-nC may be expressed as "D") and ng-nF are also expressed in the fifth decimal place. Therefore, the amount of change in nd, D, and ng-nF is expressed in the fifth decimal place.
The Abbe number νd is expressed in the second decimal place, and the amount of change in the Abbe number is also expressed in the second decimal place.
Pg and F are expressed in the fourth decimal place, and the amount of change in Pg and F is also expressed in the fourth decimal place.

The optical glass of the present invention specifically includes "first aspect" and "second aspect" optical glass, and the present invention includes these first aspect and second aspect. In the following description, the "first aspect" and the "second aspect" may be described separately.

[Optical glass characteristics]
(Partial dispersion ratio Pg, F)
The optical glass of the present invention is suitable for color correction difference correction, and is preferably one having high anomalous dispersibility. Partial dispersion ratios Pg and F are used as indicators of anomalous dispersibility.

For the partial dispersion ratios Pg and F, the refractive index nF at the F line (wavelength 486.13 nm), the refractive index nC at the C line (wavelength 656.27 nm), and the refractive index ng at the g line (wavelength 435.84 nm) are used. , Is expressed as in equation (1).
Pg, F = (ng-nF) / (nF-nC) ... (1)

In the optical glass of the present invention, it is preferable that the partial dispersion ratios Pg and F and the Abbe number νd satisfy the formula (2).
Pg, F> -0.0004νd + 0.5720 ... (2)
An optical glass in which the partial dispersion ratios Pg and F and the Abbe number νd satisfy the equation (2) can be suitably used as an optical glass for correcting higher-order chromatic aberration.

Regarding the values of Pg and F of the optical glass of the present invention, the lower limit can be 0.5200 or more, 0.5250 or more, 0.5300 or more, and the upper limit can be 0.6000 or less, 0.5950 or less, 0. It can be less than or equal to 5.900.

In the optical glass of the first aspect, the lower limit of the Pg and F values is preferably 0.545 or more, 0.550 or more, and 0.555 or more in this order, and the upper limit is 0.600 or less, 0.595 or less, 0. It is preferable in the order of 590 or less.
In the optical glass of the second aspect, the lower limit of the values of Pg and F is preferably 0.520 or more, 0.525 or more, and 0.530 or more in this order, and the upper limit is 0.570 or less, 0.565 or less, 0. It is preferable in the order of .560 or less.

(Viscosity at liquid phase temperature LT)
The optical glass of the present invention has a viscosity at a liquidus temperature LT of 10.0 dPa · s or more. When the viscosity at the liquidus temperature LT is 10.0 dPa · s or more, the veins can be suppressed when the molten glass is cast, and a homogeneous glass can be obtained.
The viscosity at the liquidus temperature LT is preferably 10.3 dPa · s or more, more preferably 10.5 dPa · s or more, further preferably 10.8 dPa · s or more, and even more preferably 11.0 dPa · s or more. In this specification, the unit of viscosity is expressed as "dPa · s", but the value is the same as "Poise".
In the present specification, the viscosity of the glass melt is determined by a co-axis double-rotating cylindrical rotational viscometer (manufactured by Tokyo Kogyo Co., Ltd., high-temperature viscosity measuring device RHEOTRONIC II (improved type)) according to the viscosity measuring method of JIS standard Z8803. ) Was used for measurement. The temperature of the optical glass as a sample was changed, the viscosity of the glass at each temperature was measured, a graph showing the relationship between the viscosity and the temperature was created, and the viscosity of the glass at the liquidus temperature was read using this graph. ..

(Liquid phase temperature LT)
The optical glass of the present invention is characterized by having a high viscosity at the liquidus temperature LT, but the liquidus temperature LT itself is not particularly limited.
The lower limit of the liquidus temperature LT of the optical glass of the present invention can be 450 ° C. or higher and 470 ° C. or higher and 480 ° C. or higher, and the upper limit can be 900 ° C. or lower, 890 ° C. or lower, or 880 ° C. or lower. ..

In the optical glass of the first aspect, the lower limit of the liquidus temperature LT is preferably 700 ° C. or higher, 720 ° C. or higher, 730 ° C. or higher, 740 ° C. or higher, and 750 ° C. or higher, and the upper limit of the liquidus temperature LT is 900 ° C. or higher. ℃ or less, 890 ° C or less, 880 ° C or less, 870 ° C or less, and 860 ° C or less are preferable in this order.
In the optical glass of the second aspect, the lower limit of the liquidus temperature LT is preferably 450 ° C. or higher, 470 ° C. or higher, 480 ° C. or higher, 490 ° C. or higher, and 500 ° C. or higher, and the upper limit of the liquidus temperature LT is 720 ° C. or higher. ℃ or less, 700 ° C or less, 690 ° C or less, 680 ° C or less, and 670 ° C or less are preferable in this order.
In the present specification, the liquidus temperature LT is determined by weighing 50 g of glass in a predetermined platinum crucible, holding the glass at a predetermined temperature for 2 hours, and then cooling the glass to room temperature, and visually and with an optical microscope the surface and the inside of the glass. The magnified observation (magnification: 100 times) was carried out to check for the presence or absence of crystal precipitation, and the lowest temperature (in 10 ° C. increments) at which no crystals were confirmed was defined as the liquidus temperature LT.

(Refractive index nd)
The refractive index nd of the optical glass of the present invention is not particularly limited.
The lower limit of the refractive index nd of the optical glass of the present invention can be 1.44000 or more, 1.44500 or more, 1.45000 or more, and the upper limit of the refractive index nd is 1.65000 or less, 1.64500 or less. , 1.64000 or less.

In the optical glass of the first aspect, the lower limit of the refractive index nd is preferably 1.57,000 or more, 1.57500 or more, 1.58000 or more, 1.58500 or more, and 1.59000 or more in this order. The upper limit of the refractive index nd is preferably 1.66000 or less, 1.65500 or less, 1.65000 or less, and 1.64500 or less in that order.
In the optical glass of the second aspect, the lower limit of the refractive index nd is preferably 1.44000 or more, 1.44500 or more, 1.45000 or more, 1.45500 or more, and 1.46000 or more in this order. The upper limit of the refractive index nd is preferably 1.48500 or less, 1.48000 or less, 1.47500 or less, and 1.47000 or less in this order.

(Abbe number νd)
The Abbe number νd of the optical glass of the present invention is not particularly limited.
The lower limit can be 44.00 or more, 44.50 or more, 45.00 or more, 45.50 or more, and the upper limit can be 86.00 or less, 85.50 or less, 85.00 or less. it can.
In the optical glass of the first aspect, the lower limit of the Abbe number νd is preferably 45.00 or more, 45.50 or more, 46.00 or more, 46.50 or more, 47.00 or more, and 47.50 or more in this order. The upper limit of the Abbe number νd is preferably 53.50 or less, 53.00 or less, 52.50 or less, 52.00 or less, and 51.50 or less in that order.
In the optical glass of the second aspect, the lower limit of the Abbe number νd is preferably 75.00 or more, 75.50 or more, 76.00 or more, 76.50 or more, 77.00 or more, and 77.50 or more in this order. The upper limit of the Abbe number νd is preferably 86.00 or less, 85.50 or less, 85.00 or less, 84.50 or less, 84.00 or less, and 83.50 or less in this order.

[Optical glass composition]
Hereinafter, the glass components that can be contained in the optical glass of the present invention will be described. The optical glass of the present invention is a fluoride-based glass, which contains at least fluorine (F), phosphorus (P), and oxygen (O).

( ^{P5 +} component)
In the optical glass of the present invention, the P ⁵⁺ component, which is an essential component, is a component that constitutes the skeleton of the glass and is a component that improves the thermal stability of the glass. It is also a component that contributes to low refractive index and low dispersion. ^{The lower limit of the P 5+} component contained in the optical glass of the present invention can be 5% or more and 7% or more, and the upper limit can be 55% or less, 50% or less, and 45% or less. In order to form a glass skeleton having a viscosity of 10.0 dPa · s or more and satisfying the formula: Pg, F> -0.0004νd + 0.5720, for example, ^{the lower limit of the P 5+} component is 5% or more and the upper limit is 55. It is preferable to set it to% or less.

In the first aspect, ^{the lower limit of P 5+} is preferably 10% or more, 15% or more, 20% or more, 22%, 25%, 28%, 29% or more, and the upper limit is 55% or less, 50%. Hereinafter, 45% or less, 42% or less, 40% or less, 39% or less, and 38% or less are preferable in this order.
In the second aspect, ^{the lower limit of P 5+} is preferably 5% or more, 6% or more, 7% or more, 8% or more, 9% or more and 10% or more, and the upper limit is 35% or less and 30% or less. , 25% or less, 20% or less, 19% or less, 18% or less, 17% or less, in that order.

(Si ⁴⁺ , B ³⁺ components)
As a component of the optical glass of the present invention, ^{in addition to the P 5+ component, a Si 4+} component and / or a B ³⁺ component can be contained as a component constituting the skeleton of the glass. The Si ⁴⁺ component and the B ³⁺ component are components that improve the thermal stability of glass and also contribute to low refractive index and low dispersion.
The content of each of the Si ⁴⁺ and B ³⁺ components is not particularly limited and can be arbitrarily contained, but the upper limit of the content is 10% or less, 5% or less, 3% or less, 1% or less, 0.1. % Or less, preferably 0%. In the present specification, 0% or more includes that the component is substantially not contained. The preferable range of the Si ⁴⁺ component and the B ³⁺ component is the same in both the first aspect and the second aspect.

The total content of Si ⁴⁺ and B ³⁺ components is also preferably 10% or less, 5% or less, 3% or less, 1% or less, 0.1% or less, and 0% in that order.

(Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ components)
The optical glass of the present invention ^{contains one or more Li +} , Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ components (these components may be hereinafter referred to as "alkali metal components"). Can be done. The Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ components are components that can improve the meltability and adjust the viscosity and refractive index of glass, but if they are too much, they become thermally unstable. May become.
The content of Li ⁺ component is not particularly limited, but the upper limit is 30% or less, 25% or less, 20% or less, 15% or less, 13% or less, 11% or less, 9.0% or less. , 7.5% or less, and 6.0% or less are preferable in this order. The lower limit is preferably 0% or more, more than 0%, 0.1% or more, 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more in this order. ..
The above-mentioned content of the Li ⁺ component is the same in both the first aspect and the second aspect.

The ^{contents of Na +} , K ⁺ , Rb ⁺ and Cs ⁺ components are also arbitrary, but the upper limit of each content is preferably 10% or less, 6.0% or less, 4.0% or less. , 3.0% or less, 2.0% or less, 1.0% or less, 0.5% or less, in that order. Both components can be 0%.
The above-mentioned contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ components are the same in both the first and second aspects. If necessary, ^{a part of the Li +} component may be replaced with another alkaline component (Na ⁺ , K ⁺ , Rb ⁺ and Cs ^{+ components).}

(Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ components)
Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ components are components that improve the meltability of glass and adjust the viscosity and refractive index of glass, but if they are too much, they become thermally unstable. There is.
The upper limit of the content of each of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ components can be 50% or less, 45% or less, 40% or less, and the lower limit of each content is, for example. , 0% or more, more than 0%, 1% or more, 3% or more.

Specifically, in the first aspect, ^{the upper limit of the content of Mg 2+} is preferably 8% or less, 6% or less, 4% or less, 2% or less, 1% or less, 0.5% or less, preferably 0. It can be% (not contained).
In the second aspect, ^{the upper limit of the content of Mg 2+} is preferably 15% or less, 10% or less, 8% or less, 7% or less, 6% or less, 5% or less in this order. The lower limit is not particularly limited, but is preferably 0% or more, more than 0%, 1.0% or more, 1.5% or more, and 2.0% or more in this order.

In ^{the first embodiment, the upper limit of Ca 2+} is preferably 10% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, and can be 0% (not contained). ..
In ^{the second aspect, Ca 2+} is not particularly limited in the upper limit, but is preferably 30% or less, 27% or less, 25% or less, 23% or less, 22% or less, 21% or less, and 20% or less in this order. The lower limit is not particularly limited, but is preferably 0% or more, more than 0%, 1.0% or more, 5% or more, 7% or more, 9% or more, 11% or more, and 12% or more in this order.

In ^{the first embodiment, the upper limit of Sr 2+} is preferably 10% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, and can be 0% (not contained).
In ^{the second aspect, Sr 2+} is preferably in the order of 30% or less, 25% or less, 23% or less, 22% or less, 21% or less, and 20% or less. The lower limit is not particularly limited, but is preferably 0% or more, more than 0%, 1.0% or more, 5% or more, 7% or more, 9% or more, 10% or more, and 11% or more in this order.

In ^{the first aspect, Ba 2+} is preferably in the order of 50% or less, 45% or less, 43% or less, 42% or less, 41% or less, 40% or less, 39% or less. The lower limit is preferably 10% or more, 15% or more, 22% or more, 25% or more, 26% or more, 27%, 28% or more, and 29% or more in this order.
In ^{the second aspect, Ba 2+} is preferably in the order of 25% or less, 23% or less, 20% or less, 18% or less, and 16% or less. The lower limit is not particularly limited, but is preferably 0% or more, 1.0% or more, 2% or more, 3% or more, and 4% or more in this order. Among them, Ba ²⁺ is a component that contributes to viscosity and high refractive index / low dispersion. Therefore, in the fluorinated optical glass of the present invention, the desired refractive index is maintained while maintaining a viscosity of 10.0 dPa · s or more. -In order to obtain the Abbe number, ^{it is preferable that Ba 2+} is 3% or more and 50% or less. Further, depending on the case, a part of ^{Ba 2+} may be replaced with ^{Mg 2+} , Ca ²⁺ , Sr ²⁺ , or Zn ^2+.

The ^{content of the Zn 2+} component is also arbitrary, but the upper limit of each content is preferably 10% or less, 6.0% or less, 4.0% or less, 3.0% or less, 2. It is preferable in the order of 0% or less, 1.0% or less, and 0.5% or less. It can also be 0%.
The above-mentioned content of the Zn ²⁺ component is the same in both the first aspect and the second aspect.

The lower limit of the total content of each of the Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ^{2+ components (Mg 2+} + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ ) is, for example, 15% or more, 20% or more, 25%. As mentioned above, it can be 27% or more, 28% or more, 29% or more, and the upper limit can be 60% or less, 55% or less, 52% or less, 50% or less, 48% or less.
The ^{possible values of the total content of Mg 2+} + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ components are the same in both the first and second aspects.

(La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ components)
The La ³⁺ , Gd ³⁺ , Y ^3+, and Yb ³⁺ components are ^{components that increase the refractive index as compared with the Mg 2+} , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ components, and contribute to high refractive index and low dispersion. However, if it is too much, the meltability may deteriorate. The content of each of the La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ components is not particularly limited, and the upper limit of the content of each of the La 3+} , Gd ³⁺ , Y ³⁺ and Yb ³⁺ components is, for example, 20% or less. It may be 10% or less, 7% or less, and 5% or less. The lower limit is not particularly limited and can be 0% or more.
In particular, ^{regarding the content of the Y 3+} component, in the first aspect, the upper limit is preferably 20% or less, 10% or less, 7% or less, 5% or less, and may be 0% (not contained). it can.
Regarding the content of the Y ³⁺ component, in the second aspect, the upper limit may be 20% or less, 10% or less, 7% or less, and 5% or less. The lower limit is not particularly limited, and is preferably 0% or more, more than 0%, 0.5% or more, and 1.0% or more in this order.

The total content of La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ^{3+ components (La 3+} + Gd ³⁺ + Y ³⁺ + Yb ³⁺ ) is also not particularly limited, and ^{the upper limit of La 3+} + Gd ³⁺ + Y ³⁺ + Yb ³⁺ is, for example, 20% or less. It may be 10% or less, 7% or less, and 5% or less.

(Ti ⁴⁺ component)
The Ti ⁴⁺ component is a component that contributes to high refractive index and high Pg and F, but if it is too large, it may be highly dispersed.
The ^{upper limit of the content of the Ti 4+} component is preferably 20% or less, 10% or less, 5% or less, 4% or less, 3% or less, and may be 0% (not contained). Only in the second aspect, the lower limit can be set to 1.0% or more.

(Nb ⁵⁺ component)
Nb ⁵⁺ is a component that contributes to high refractive index and high Pg and F, but if it is too much, it may be highly dispersed.
The ^{upper limit of the content of the Nb 5+} component is preferably 30% or less, 20% or less, 15% or less, 14% or less, 13% or less, and may be 0% (not contained). In the first aspect, the lower limit is preferably 1% or more, 3% or more, and 5% or more in that order.
In the futurate-based glass of the present invention, ^{the upper limit of the content of Ti 4+} component is set to the above value, and / or ^{the upper limit of the content of Nb 5+} component is set to the above value, so that the values of Pg and F become ". It becomes easy to set so as to exceed the value of "-0.0004νd + 0.5720". For example, by ^{setting the content of the Ti 4+} component to 20% or less and / or ^{the content of the Nb 5+} component to 30% or less, the values of Pg and F exceed the value of "-0.0004νd + 0.5720". It becomes easy to set to.

The Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ components are components that contribute to high refractive index and high Pg and F, but if they are too large, they may be highly dispersed. These components can be contained within a range that does not impair the characteristics of the optical glass of the present invention. The content of each of the Ta ⁵⁺ , W ⁶⁺ and Bi ³⁺ components is not particularly limited, and the upper limit of each content is 10% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1%. It can be as follows, and can be 0% (not contained).

The total content of each of the Ta ⁵⁺ , W ⁶⁺ and Bi ^{3+ components (Ta 5+} + W ⁶⁺ + Bi ³⁺ ) is also not particularly limited, and the upper limit is 10% or less, 5% or less, 4% or less, 3% or less, 2 It can be% or less and 1% or less. The lower limit can be 0% or more.

The optical glass of the present invention preferably contains ^{Ti 4+} and / or Nb ^5+. In ^{the case of optical glass having anomalous dispersibility, Ti 4+} and Nb ⁵⁺ may be able to increase Pg and F by adding them. By adding these components, it may be possible to obtain high Pg and F that satisfy the formula (1), which is preferable.

When the optical glass of the present invention contains the P ⁵⁺ component and the Ti ⁴⁺ component, the molar ratio (O ^2- / (P ⁵⁺ + Ti ⁴⁺ )) of the ^{O 2-} component and the P ⁵⁺ component + Ti ^{4+ component is volatile.} From the viewpoint of suppression, the order is preferably 3.0 or more, 3.1 or more, 3.2 or more, and the upper limit is 4.0 or less, 3.9 or less, 3.8 or less from the viewpoint of thermal stability of glass. Preferable in order. The molar ratio (O ² / / (P ⁵⁺ + Ti ⁴⁺ )) is calculated from the value of atomic% (atom%).

When the optical glass of the present invention contains the P ⁵⁺ component and the Nb ⁵⁺ component, the molar ratio (O ^2- / (P ⁵⁺ + Nb ⁵⁺ )) of the ^{O 2-} component and the P ⁵⁺ component + Nb ^{5+ component is volatile.} From the viewpoint of suppression, the order is preferably 3.0 or more, 3.1 or more, 3.2 or more, and the upper limit is 4.0 or less, 3.9 or less, 3.8 or less from the viewpoint of thermal stability of glass. Preferable in order. The molar ratio (O ^2- / (P ⁵⁺ + Nb ⁵⁺ )) is also calculated from the atomic% (atom%) value.

(Al ³⁺ component)
The Al ³⁺ component is a component that improves the chemical durability, and when introduced, the thermal stability of the glass may be improved. In addition, Al ³⁺ may have a function of improving workability. If it is contained in an excessive amount, the meltability may deteriorate. The content of the Al ³⁺ component is also not particularly limited, but from the viewpoint of meltability, ^{the upper limit of the content of each of the Al 3+} components can be, for example, 50% or less, 45% or less, 40% or less, and the lower limit is It can be 5% or more, 8% or more, and 10% or more. For example, ^{by containing 5% or more and 50% or less of the Al 3+} component, the futurate-based glass of the present invention is imparted with good chemical durability, and in some cases, it is made difficult to devitrify. The production of the glass can be facilitated in a stable manner.

In the first aspect, ^{the upper limit of the Al 3+} component is preferably 30% or less, 25% or less, 22% or less, 21% or less, 20% or less, and the lower limit is 5% or more, 8% or more, 10% or more. , 12% or more, and 13% or more are preferable in this order.
Specifically, in the second aspect, ^{the upper limit of the Al 3+} component is preferably 50% or less, 45% or less, 42% or less, 40% or less, and 38% or less, and the lower limit is 10% or more and 12%. Above, 15% or more, 17% or more, and 20% or more are preferable in this order.

The ratio of P ⁵⁺ to Al ³⁺ is not particularly limited, and the effect can be confirmed for both optical glass having a relatively large amount of ^{P 5+ and glass having a relatively large amount of Al 3+.}

(Zr ⁴⁺ component)
The Zr ⁴⁺ component is also a component that improves chemical durability, and when introduced, it may improve the thermal stability of the glass. The optical glass of the present invention can contain a small amount, but it is excessive. If it is contained, the meltability may be deteriorated. Therefore, ^{the upper limit of the content of each of the Zr 4+} components is, for example, 10% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0. It may be 5% or less, and can be 0% (not contained).
The ^{possible content of the Zr 4+} component is the same in both the first and second aspects.

If desired, at least one cation of As, Sb and Sn can be added to the glass. The cations of As, Sb and Sn have a clarification effect at the time of glass melting and an effect of reducing platinum particles in the obtained glass. In some cases, the oxidation / reduction state of glass can be adjusted. The contents of the cations of As, Sb and Sn are not particularly limited, but the upper limits of the contents of the cations of As, Sb and Sn are 1% or less, 0.9% or less and 0.8. % Or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, 0.09% or less , 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less, 0 .009% or less, 0.008% or less, 0.007% or less, 0.006% or less, 0.005% or less, 0.004% or less, 0.003% or less, 0.002% or less, 0.001 It may be less than or equal to%. The lower limit of the content of each of As, Sb and Sn cations is 0% or more, 0.001% or more, 0.002% or more, 0.003% or more, 0.004% or more, 0.005%. Above, 0.006% or more, 0.007% or more, 0.008% or more, 0.009% or more, 0.01% or more, 0.02% or more, 0.03% or more, 0.04% or more, 0.05% or more, 0.06% or more, 0.07% or more, 0.08% or more, 0.09% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0. It may be 4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more. It can also be absent.
The possible contents of the As, Sb and Sn components are the same in both the first aspect and the second aspect.

(F ^- component)
The optical glass of the present invention contains ^{fluorine (F −) as an anion component.} The content of F ⁻ is not particularly limited, but can be 90% or less, 85% or less, 80% or less, and ^{the lower limit of the F −} content is 10% or more and 15%. As mentioned above, it can be 20% or more.

^{Specifically, the upper limit of the F −} content in the first aspect is preferably 50% or less, 45% or less, 43% or less, 40% or less, 39% or less, and the lower limit is 15% or more. , 20% or more, 22% or more, 25% or more, and 27% or more are preferable in this order.
^{The upper limit of the F −} content in the second aspect is preferably 90% or less, 85% or less, 83% or less, 80% or less, 78% or less, and the lower limit is 60% or more and 62%. Above, 65% or more, 68% or more, 70% or more, 72% or more are preferable in this order.

^{(Cl -, Br -, I} - component)
The optical glass of the present invention can contain halogen ions such as ^{Cl −} , Br ⁻ , and I ⁻ in addition to ^{F −.} The upper limit of each content can be 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, 0.5% or less, and 0% (not contained). ..

Among these, F ⁻ and Cl ⁻ have a function of lowering the dispersion by introduction, a function of imparting anomalous dispersibility of glass, a function of lowering the glass transition temperature, and a function of improving chemical durability. There is.

If it is a problem that the material contains radioactive substances depending on the application, it is preferable to keep the content of radioactive isotopes below a certain amount or intentionally not to contain them (however, it does not prevent contamination as impurities). ).

[Manufacturing method of optical glass]
The optical glass of the present invention can be obtained, for example, by blending, melting, and molding a glass raw material so that predetermined characteristics can be obtained. As the glass raw material, for example, phosphate, fluoride, alkali metal compound, alkaline earth metal compound may be used. As for the glass melting method and molding method, a known method may be used.

The "predetermined temperature" of the melting of the present invention is a temperature at which the glass can be completely melted. The specific predetermined temperature is (A) 950 ° C. or (B) the liquid phase temperature of the glass (hereinafter sometimes referred to as LT) + 150 ° C. to 400 ° C. (150 ° C. for LT). The added temperature to the temperature obtained by adding 400 ° C. to LT). Therefore, the predetermined temperature satisfies either (A) or (B) above. Specific predetermined temperatures include, for example, 850, 900 ° C, 950 ° C, 1000 ° C, 1050 ° C, 1100 ° C, 1150 ° C and the like.

The atmosphere in melting the optical glass of the present invention can be an atmosphere, a non-oxidizing atmosphere, a reducing atmosphere, etc., but melting is performed in a non-oxidizing atmosphere (specifically, N ₂ atmosphere, Ar atmosphere, etc.). It is preferable to do so.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the Examples.

(Measurement of optical glass characteristics)
Using raw materials such as optical glass grade high-purity oxides, hydroxides, carbonates, nitrates, chlorides, fluorides, and sulfates, glasses having the compositions of Examples and Comparative Examples in Table 1 can be obtained. The raw materials were weighed and mixed so as to be used as a compounding raw material. Next, each compounded raw material is placed in a platinum crucible, heated to a predetermined temperature as described above, melted in a nitrogen atmosphere for 2 hours or 4 hours from the start of melting, and then stirred and homogenized. After allowing to stand and clarifying, it was poured into a mold. After the glass solidified, it was then transferred to an electric furnace heated near the slow cooling point of the glass and slowly cooled to room temperature. In this way, a block made of glass of each Example / Comparative Example was produced. A test piece necessary for measurement was cut out from each of the obtained glass blocks, polished, and evaluated for characteristics.

(1) Measurement of nd, ng, nF, nC and Abbe number νd The refractive index nd, ng, nF of the glass obtained by lowering the temperature at a temperature lowering rate of −30 ° C./hour according to the refractive index measurement method of JIS B 7071. , NC and Abbe number νd were measured.

(2) Measurement of partial dispersion ratios Pg and F The partial dispersion ratios Pg and F were calculated from the nd, ng, nF and nC obtained in (1) above.

The compositions of the optical glasses used in Examples and Comparative Examples are shown in Table 1 (notation by cation% (cat.%) And anion% (ani.%)) And Table 2 (notation by atomic% (atom.%)). , Table 3 shows the characteristics of each optical glass. The values of nd, νd, Pg, and F in Table 3 are the values when the glass is melted for 1.5 hours.

The LT (liquid phase temperature) and LT viscosity (viscosity at the liquid phase temperature) in Table 2 are values measured by the method described in the specification. The optical glass used for the measurement was 50 g in the case of the liquidus temperature LT measurement, and the glass volume was in the range of 12.5 ml ± 2.0 ml. The LT viscosity was measured with a glass volume of 20 to 25 cc.

Further, a photograph when the optical glass obtained in Example 1 is polished is shown in FIG. 1, and a photograph when the optical glass obtained in Comparative Example 2 is polished is shown in FIG. Since the optical glass of Comparative Example 2 has a low LT viscosity, veins were found due to the influence of convection and the like during casting. On the other hand, the optical glass of FIG. 1 has extremely few veins and is useful as an optical glass.

The optical glass of the present invention can be used as a material for an optical element.

Claims (6)

A fluorinated optical glass having a viscosity at a liquidus temperature of 10.0 dPa · s or more and satisfying Pg, F> -0.0004νd + 0.5720. The optical glass according to claim 1, wherein the refractive index (nd) is 1.45000 or more and 1.65000 or less, and the Abbe number (νd) is 45.0 or more and 85.0 or less. The optical glass according to claim 1 or 2, which contains a component in the following range in% cation;
P ^{5 +} 5% or more, 55% or less,
Al ³⁺ 5% or more, 50% or less,
Ba ²⁺ 3% or more, 50% or less. The optical glass according to any one of claims 1 to 3, which contains 20% or less of Ti ^{4+ in% cation.} The optical glass according to any one of claims 1 to 4, which contains 30% or less of Nb ^{5+ in% cation.} The optical element made of the optical glass according to any one of claims 1 to 5.

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