CN113636754A

CN113636754A - Fluorophosphoric acid optical glass for large-volume pressing for sheet molding, optical element, preform, and lens

Info

Publication number: CN113636754A
Application number: CN202110494803.7A
Authority: CN
Inventors: 小栗史裕; 永岛莉那
Original assignee: Ohara Inc
Current assignee: Ohara Inc
Priority date: 2020-05-11
Filing date: 2021-05-07
Publication date: 2021-11-12
Also published as: TW202142511A

Abstract

The invention provides a glass sheet which has desired optical characteristics and can be reduced even when the glass sheet is a thin sheetA fluorophosphate optical glass for sheet press molding which is obtained stably while causing a small amount of glass breakage and cracking during press molding. The fluorophosphoric acid optical glass for sheet molding, expressed in cation% (mol%): p⁵⁺From 17.0% to 42.0% of La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺A total content (Ln) of 1 or more selected from the group³⁺: cation%) 13.0% or less, from Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺A total content R of 1 or more selected from the group consisting of²⁺(cation%) with Al³⁺Ratio of content (cation%) (R)²⁺/Al³⁺) At 1.50 or more and at 4.00 or less; expressed as anionic% (mol.%), F^－The content of (A) is 30.0 to 60.0%; and has the desired optical characteristics.

Description

Fluorophosphoric acid optical glass for large-volume pressing for sheet molding, optical element, preform, and lens

Technical Field

The present invention relates to a fluorophosphate optical glass for sheet molding, a fluorophosphate optical glass for multi-volume molding, an optical element, a preform, and a lens.

Background

In recent years, digitalization and high definition of devices using an optical system have been rapidly advanced, and in the fields of various optical devices such as a camera, a video camera, a mobile phone with a camera, and the like, and an image display (projection) device such as a projector, a projection television, and the like, there has been an increasing demand for reducing the number of optical elements such as lenses, prisms, and the like used in the optical system, and for reducing the weight and size of the entire optical system.

In particular, since the production of an aspherical lens by grinding and polishing methods is costly and inefficient, a precision press molding method can be used as a method for producing an aspherical lens, in which a preform material obtained by cutting and polishing a glass gob (gob) or a glass block is heated and softened and the preform is press-molded by using a molding die having a highly precise surface, whereby grinding and polishing steps can be omitted, and a low-cost and large-scale production can be realized.

In recent years, optical elements have been produced by a multi-press (multi-press) technique for mass-producing a plurality of optical elements by using a mold capable of transferring a thin plate of optical glass or the like into a plurality of lens shapes, and there has been a demand for optical glass used as a material for performance that has not been required in the past, such as temperature change during pressing, pressure, and compatibility with the mold.

The material constituting the optical element of the optical system has a refractive index (n) of 1.48000 or more and 1.58000 or less_d) And an Abbe number (. nu.) of 68.00 or more and 88.00 or less_d) The demand for so-called high-refractive-index low-dispersion glasses is still increasing. Such a glass may be exemplified by a glass having P as a main component⁵⁺And contains a large amount of F^－As the fluorophosphate glass, for example, a glass composition as represented in patent document 1 is known. If such a low dispersion glass useful for optical design is suitable for precision press molding or large-volume press molding as described above, the overall weight reduction and size reduction of the optical system can be achieved while satisfying the optical design requirements.

Further, as a material of an optical element constituting an optical system, a lens made of a curable resin is highly demanded because of a lower transition point and excellent workability as compared with a lightweight glass. As such a glass, for example, a resin composition as represented in patent document 2 is known.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-208842

Patent document 2: japanese Kokai publication WO 2014-119424

Disclosure of Invention

Technical problem to be solved by the invention

However, in the fluorophosphate glass described in patent document 1, when a large amount of the glass is pressed after lens processing, F is caused^－The content of (b) is large, so that the glass surface is fogged, and cracks or fissures may occur due to the difference in thermal expansion between the mold and the glass.

The curable resin described in patent document 2 has a narrower range of optical constants than glass, and in particular, it is difficult to have a refractive index (n) of 1.48000 or more and 1.58000 or less_d) And an Abbe number (. nu.) of 68.00 or more and 88.00 or less_d)。

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fluorophosphate optical glass for sheet molding, a fluorophosphate optical glass for mass production, and an optical element, a preform, and a lens using the same, which have desired optical characteristics, can reduce breakage and cracking of glass at the time of mass production press molding, and can stably obtain glass.

Means for solving the problems

The present inventors have conducted extensive experimental studies to solve the above-mentioned problems, and as a result, have found that P is contained in a glass⁵⁺、F^－The present inventors have found that the glass composition can have a desired refractive index and abbe number by adjusting the content of each component as a cation component and an anion component, and that cracking and crazing of the glass during press molding can be reduced even when the glass is a thin plate, and that the glass can be stably obtained, thereby completing the present invention. Specifically, the present invention provides the following products.

(1) A fluorophosphoric acid optical glass for sheet press molding, expressed in cation% (mol%):

P⁵⁺at least 17.0% and at most 42.0%,

from La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺A total content Ln of 1 or more selected from the group³⁺(cation%) is less than 13.0%,

from Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺A total content R of 1 or more selected from the group consisting of²⁺(cation%) with Al³⁺Ratio of content (cation%) (R)²⁺/Al³⁺) At 1.50 or more and at 4.00 or less;

expressed as anionic% (mol%):

F^－the content of (A) is 30.0 to 60.0%;

refractive index (n)_d) Is not less than 1.48000 and not more than 1.58000,

abbe number (v)_d) In the range of 68.00 or more and 88.00 or less,

a partial dispersion ratio (θ g, F) of 0.5290 or more,

F^－the ratio (F) of the content (anion%) of (a) to the partial dispersion ratio (θ g, F)^－(theta g, F)) is 105 or less, and the maximum value of the linear expansion coefficient (alpha)_max) Is 1300 x 10^－7K^－1The following.

(2) An optical glass as described in (1), wherein Ca²⁺Content ratio (% cation) and R²⁺(cation%) ratio (Ca)² ⁺/R²⁺) Above 0.18.

(3) The optical glass according to (1) or (2), wherein the difference between the glass transition point (Tg) and the yield point (At) is 45 ℃ or less.

(4) A fluorophosphoric acid optical glass for multiple press, expressed in terms of cation% (mol%):

P⁵⁺at least 17.0% and at most 42.0%,

expressed as anionic% (mol%):

F^－the content of (A) is 30.0 to 60.0%;

refractive index (n)_d) Is not less than 1.48000 and not more than 1.58000,

abbe number (v)_d) In the range of 68.00 or more and 88.00 or less,

a partial dispersion ratio (θ g, F) of 0.5290 or more,

(5) The fluorophosphoric acid optical glass according to (4), wherein Ca²⁺Content ratio (% cation) and R²⁺(cation%) ratio (Ca)²⁺/R²⁺) Above 0.18.

(6) The fluorophosphate optical glass according to (4) or (5), wherein the difference between the glass transition point (Tg) and the yield point (At) is 45 ℃ or less.

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

(8) A preform for polishing and/or precision press molding made of the glass described in any one of (1) to (6).

(9) A lens made of the optical element as described in (7).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a fluorophosphoric acid optical glass for thin plate press molding, a fluorophosphoric acid optical glass for large volume press molding, and an optical element, a preform, and a lens using the same, which have optical characteristics of high refractive index and low dispersion, can reduce breakage and cracking of glass in large volume press molding even when the glass is a thin plate, and are stable.

Drawings

FIG. 1 is a photograph of the surface of a glass of example 2 of the present application taken at a magnification of 50 times using ECLIPSE-LV 100 manufactured by Nikon K.K.

FIG. 2 is a photograph of the surface of a glass of comparative example 3 of the present application taken at a magnification of 50 times using ECLIPSE-LV 100 manufactured by Nikon K.K.

FIG. 3 shows the partial dispersion ratio (. theta.g, F) and Abbe number (. nu.) of a glass of an example of the present invention_d) A graph of the relationship of (1).

Detailed Description

The fluorophosphoric acid optical glass for sheet press molding and the fluorophosphoric acid optical glass for large-amount press molding of the present invention are expressed by cation% (mol%): p⁵⁺From 17.0% to 42.0% of La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺A total content Ln of 1 or more selected from the group³⁺(cation%) is less than 13.0%, and Mg is selected from²⁺、Ca²⁺、Sr²⁺And Ba²⁺A total content R of 1 or more selected from the group consisting of²⁺(cation%) with Al³⁺Ratio of content (cation%) (R)²⁺/Al³⁺) At 1.50 or more and at 4.00 or less; expressed as anionic% (mol%): f^－The content of (A) is 30.0 to 60.0%; refractive index (n)_d) Has an Abbe number (v) of 1.48000 or more and 1.58000 or less_d) In the range of 68.00-88.00, the partial dispersion ratio (theta g, F) is 0.5290-F^－The ratio (F) of the content (anion%) of (a) to the partial dispersion ratio (θ g, F)^－(theta g, F)) is 105 or less, and the maximum value of the linear expansion coefficient (alpha)_max) Is 1300 x 10^－7K^－1The following. By making the glass contain P⁵⁺、F^－The fluorophosphoric acid optical glass for thin plate molding, the fluorophosphoric acid optical glass for large amount pressing, and the optical element, the preform and the lens using the same can be obtained, which have optical characteristics of high refractive index and low dispersion, can reduce the breakage and crack of the glass during the large amount pressing even if the glass is a thin plate, and are stable.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention. Note that, description of parts overlapping with the description may be omitted as appropriate, and this does not limit the interest of the invention.

< glass component >

The respective components constituting the optical glass of the present invention will be explained.

In the present specification, unless otherwise specified, the content of each component is entirely expressed by cation% or anion% based on the molar ratio. The terms "cation%" and "anion%" (hereinafter sometimes referred to as "cation% (mol%)" and "anion% (mol%)") are used to indicate the content of each component contained in the glass by separating the glass composition components of the optical glass of the present invention into a cation component and an anion component and making the total ratio of each component 100 mol%.

Note that the ion valences of the respective components are merely representative values for convenience, and are not distinguished from other ion valences. The ion valence of each component present in the optical glass may be a value other than the representative value. For example, P is usually present in the glass in a state of ionic valence 5, and hence "P" is used in the present specification⁵⁺"indicates, but may exist in other ionic valence states. Although it is possible to exist in other states of ion valence strictly speaking, in the present specification, each component is present in the glass at the ion valence representing the value.

[ regarding the cationic component ]

P⁵⁺The glass forming component has the properties of reducing devitrification of the glass and improving the refractive index. Thus, P⁵⁺The content of (b) is preferably 17.0% or more, more preferably 20.0% or more, still more preferably 23.0% or more, further preferably 26.0% or more, and most preferably 28.0% or more.

On the other hand, by adding P⁵⁺The content of (b) is reduced to 42.0% or less, the linear expansion coefficient of the glass and the maximum value of the linear expansion coefficient can be reduced, and the abbe number can be increased. Thus, P⁵⁺The upper limit of the content of (b) is preferably 42.0%, more preferably 39.0% or less, still more preferably 36.0% or less, and further preferably 33.0% or less.

Al³⁺The glass has the properties of reducing devitrification of the glass, reducing the coefficient of linear expansion and improving the Abbe number. Thus, Al³⁺The content of (b) is preferably 7.0% or more, more preferably 9.0% or more, still more preferably 11.0% or more, further preferably 13.0% or more, and still further preferably 15.0% or more.

On the other hand, by mixing Al³⁺Is composed ofWhen the ratio is reduced to 30.0% or less, the refractive index can be increased and the maximum value of the linear expansion coefficient of the glass can be reduced. Thus, Al³⁺The upper limit of the content of (b) is preferably 30.0%, more preferably 27.0% or less, still more preferably 25.0% or less, still more preferably 23.0% or less, and still more preferably 21.0% or less.

Mg²⁺And has the properties of reducing devitrification of the glass and lowering the linear expansion coefficient and the maximum value of the linear expansion coefficient. Thus, Mg²⁺The lower limit of the content of (b) is preferably more than 0%, more preferably 1.0% or more, still more preferably 3.0% or more, further preferably 5.0% or more, and still further 5.5% or more.

On the other hand, by adding Mg²⁺In the range of 22.0% or less, the partial dispersion ratio (θ g, F) can be suppressed from decreasing, and devitrification due to an excessive content can be reduced, and a desired high refractive index can be easily obtained. Thus, Mg²⁺The upper limit of the content of (b) is preferably 22.0%, more preferably 20.0% or less, still more preferably 17.0% or less, still more preferably 15.0% or less, and still more preferably 13.0% or less.

Ca²⁺The composition has the properties of reducing devitrification and suppressing a decrease in refractive index. Thus, Ca²⁺The lower limit of the content of (b) is preferably more than 0%, more preferably 1.0% or more, still more preferably 3.0% or more, further preferably 5.0% or more, and most preferably 8.0% or more.

On the other hand, by mixing Ca²⁺The content of (b) is reduced to 25.0% or less, so that the partial dispersion ratio (θ g, F) can be suppressed from decreasing, and devitrification due to an excessive content can be reduced, and a desired high refractive index can be easily obtained. Thus, Ca²⁺The upper limit of the content of (b) is preferably 25.0%, more preferably 22.0% or less, still more preferably 20.0% or less, further preferably 17.0% or less, and most preferably 15.0% or less.

Sr²⁺When the content is more than 0%, the glass has the properties of reducing devitrification, suppressing lowering of refractive index, and reducing the maximum value of the linear expansion coefficient. Thus, Sr²⁺The content of (b) is preferably more than 0%, more preferably 1.0% or more, still more preferably 3.0% or more, and further preferably 5.0% or more.

On the other hand, by reacting Sr²⁺The content of (b) is reduced to 30.0% or less, so that devitrification due to an excessive content can be reduced, and a desired high refractive index can be easily obtained. Thus, Sr²⁺The upper limit of the content of (b) is preferably 30.0%, more preferably 25.0% or less, still more preferably 21.0% or less, and further preferably 18.0% or less.

Ba²⁺The glass has properties of improving the resistance to devitrification, increasing the partial dispersion ratio (θ g, F), reducing the maximum value of the linear expansion coefficient, maintaining low dispersion, and improving the refractive index. Thus, Ba²⁺The content of (b) is preferably more than 0%, more preferably 1.0% or more, still more preferably 3.0% or more, further preferably 5.0% or more, and further more preferably 8.0% or more.

On the other hand, by mixing Ba²⁺The content of (2) is reduced to 35.0% or less, whereby the resistance to devitrification of the glass is improved, and the linear expansion coefficient and the specific gravity are reduced. Thus, Ba²⁺The upper limit of the content of (b) is preferably 35.0%, more preferably 32.0% or less, still more preferably 30.0% or less, still more preferably 27.0% or less, and still more preferably 25.0% or less.

La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺Is an optional component, and when the content of at least one of them is more than 0%, the composition can maintain a low dispersibility (high abbe number), increase the refractive index, and further improve resistance to devitrification. In particular, Gd³⁺And Y³⁺The content of one or both of them is preferably more than 0%, more preferably 0.3% or more, and still more preferably 0.5% or more.

On the other hand, by mixing La³⁺、Yb³⁺And Lu³⁺The content of at least one of them is reduced to 10.0% or less, or Gd is added³⁺And Y³⁺One ofOr both of them are reduced to a content of 12.0% or less, and devitrification due to an excessive content of these components can be reduced, and the increase of the glass transition point and the yield point can be suppressed. Thus, La³⁺、Yb³ ⁺And Lu³⁺The upper limit of the content of (b) is preferably 10.0%, more preferably 5.0% or less, and still more preferably 3.0% or less, respectively. In addition, Gd³⁺And Y³⁺The upper limit of the content of one or both of them is preferably 12.0%, more preferably 10.0% or less, still more preferably 7.0% or less, still more preferably 4.0% or less, still more preferably 3.0% or less, and still more preferably 2.5% or less.

Zn²⁺When the content is more than 0%, the linear expansion coefficient of the glass and the maximum value of the linear expansion coefficient are reduced, the glass transition point is lowered, and the devitrification resistance and the acid resistance of the glass are improved. Thus, Zn²⁺The content of (b) is preferably more than 0%, more preferably 0.2% or more, and still more preferably 0.5% or more.

On the other hand, by adding Zn²⁺The content of (2) is reduced to 13.0% or less, and a desired low Abbe number can be easily obtained. Thus, Zn²⁺The upper limit of the content of (b) is preferably 13.0%, more preferably 12.0% or less, still more preferably 10.0% or less, further preferably 8.0% or less, and most preferably 5.0% or less.

Li⁺、Na⁺And K⁺And (d) is an optional component, and when the content of at least one of the components is more than 0%, the glass composition has a property of reducing the glass transition point (Tg) while maintaining resistance to devitrification at the time of glass formation.

On the other hand, by mixing Li⁺、Na⁺And K⁺The chemical durability can be improved by reducing the content of at least one of them to 10.0% or less. In particular, Li⁺Has the effect of reducing the partial dispersion ratio (θ g, F). Thus, Li⁺、Na⁺And K⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, and still more preferably less than 3.0%, is more preferably less than 2.0%, still more preferably less than 1.0%, and still more preferably 0.3% or less. In addition, Li may not be contained⁺、Na⁺And K⁺At least any one of them.

Si⁴⁺And is an optional component, and when the content is more than 0%, the glass has properties of improving resistance to devitrification, improving refractive index, and reducing abrasion.

On the other hand, by mixing Si⁴⁺The content of (B) is reduced to 10.0% or less, and Si can be reduced⁴⁺An excessive content of (b) causes devitrification of the glass. Thus, Si⁴⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, and most preferably not contained.

B³⁺And is an optional component, and when the content is more than 0%, the glass has properties of improving resistance to devitrification, improving refractive index, and reducing abrasion.

On the other hand, by mixing B³⁺The content of (2) is reduced to 10.0% or less, and the chemical durability of the glass can be improved. Thus, B³⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, and most preferably not contained.

Ti⁴⁺、Nb⁵⁺And W⁶⁺And is an optional component, and has a property of increasing the refractive index of the glass when the content of at least any one of them is more than 0%. Further, Nb⁵⁺Is a component having a property of improving chemical durability, W⁶⁺Is a component having a property of lowering the glass transition point.

On the other hand, by mixing Ti⁴⁺、Nb⁵⁺And W⁶⁺The content of at least one of them is reduced to 10.0% or less, and a desired high Abbe number can be easily obtained. Further, by adding Ti⁴⁺And W⁶⁺When the content of (b) is reduced to the above range, the coloring of the glass can be reduced. Thus, Ti⁴⁺、Nb⁵⁺And W⁶⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and further preferably less than 1.0%, respectively.

Zr⁴⁺And is an optional component, and when the content is more than 0%, the refractive index of the glass can be increased.

On the other hand, by adding Zr⁴⁺The content of (b) is reduced to 10.0% or less, and the texture due to volatilization of components in the glass can be reduced. Thus, Zr⁴⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and still more preferably less than 1.0%.

Ta⁵⁺And is an optional component, and when the content is more than 0%, the refractive index of the glass can be increased.

On the other hand, by mixing Ta⁵⁺The content of (b) is reduced to 10.0% or less, and devitrification of the glass can be reduced. Thus, Ta⁵⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and still more preferably less than 1.0%.

Ge⁴⁺And is an optional component, and when the content is more than 0%, the refractive index of the glass can be increased and resistance to devitrification can be improved.

On the other hand, by adding Ge⁴⁺The content of (2) is reduced to 10.0% or less, and the material cost of the glass can be reduced. Thus, Ge⁴⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and still more preferably less than 1.0%.

Bi³⁺And Te⁴⁺And is an optional component, and when the content is more than 0%, the refractive index of the glass can be increased and the glass transition point can be lowered.

On the other hand, by adding Bi³⁺And Te⁴⁺The content of at least one of them is reduced to 10.0% or less, and the coloring and devitrification of the glass can be reduced. Thus, it is possible to provide，Bi³⁺And Te⁴⁺The upper limit of the content of (b) is preferably 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and further preferably less than 1.0%, respectively.

[ regarding the anionic component ]

F^－The glass has the properties of improving the abnormal dispersibility and Abbe number of the glass, reducing the glass transition point and making the glass difficult to devitrify. Thus, F^－The content of (b) is preferably 30.0% or more, more preferably 33.0% or more, still more preferably 37.0% or more, and further preferably 40.0% or more.

On the other hand, F^－When the content is large, the Abbe number of the glass is excessively increased and the refractive index is lowered. In particular, in the present invention, when F^－When the content of (A) is large, F is used in the case of mass molding^－Can lead to fogging. Thus, F^－The content of (b) is preferably 60.0% or less, more preferably 57.0% or less, still more preferably 55.0% or less, and further preferably 53.0% or less.

O^2－The glass composition has the properties of inhibiting devitrification of glass and inhibiting increase in abrasion. Thus, O^2－The content of (b) is preferably 40.0% or more, more preferably 43.0% or more, still more preferably 45.0% or more, and further preferably 47.0% or more.

On the other hand, although the effect of other anion components is more easily obtained, the partial dispersion ratio (θ g, F) is lowered, and therefore O^2－The content of (b) is preferably 70.0% or less, more preferably 67.0% or less, still more preferably 63.0% or less, and further preferably 60.0% or less.

Further, from the viewpoint of suppressing devitrification of glass, O is^2－Content ratio of (A) and (F)^－The lower limit of the total content of (b) is preferably 98.0%, more preferably 99.0%, and still more preferably 100%. I.e. except O^2－And F^－Other anionic components, e.g. from Cl^－、Br^－、I^－The total content of 1 or more selected from the group consisting ofIs preferably 2.0%, more preferably 1.0%, most preferably 0%.

R²⁺Refers to the form of Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺1 or more selected from the group consisting of. In addition, R²⁺The total content of (A) is derived from Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺A total of 1 or more selected from the group consisting of.

Here, by making R²⁺The total content of (A) is in the range of 34.0 to 63.0%, and glass having higher devitrification resistance can be obtained.

Thus, R²⁺The lower limit of the total content of (b) is preferably 34.0% or more, more preferably 37.0% or more, still more preferably 40.0% or more, further preferably 43.0% or more, and most preferably 46.0% or more. In addition, R²⁺The upper limit of the total content of (b) is preferably 63.0% or less, more preferably 60.0% or less, still more preferably 57.0% or less, and further preferably 54.0% or less.

In the optical glass of the present invention, Ca²⁺Content ratio (% cation) and R²⁺The ratio (Ca) of the total content (cation%) of (C)²⁺/R²⁺) Preferably 0.18 or more.

R²⁺Of middle, Ca²⁺In particular, the maximum value of the linear expansion coefficient can be reduced, and thus the ratio (Ca) can be set to be smaller²⁺/R²⁺) Being 0.18 or more, the maximum value of the linear expansion coefficient can be further reduced. Thus, the ratio (Ca)²⁺/R²⁺) The lower limit of (b) is preferably 0.18 or more, more preferably 0.19 or more, and still more preferably 0.20 or more.

In another aspect, R²⁺Of middle, Ca²⁺Has a property of reducing a partial dispersion ratio (θ g, F), and thus the ratio (Ca)²⁺/R²⁺) Preferably 0.50 or less, more preferably 0.45 or less, still more preferably 0.40 or less, further preferably 0.35 or less, and still further preferably 0.33 or less.

In the optical glass of the present invention, R²⁺The total content (cation%) of (A) and Al³⁺Having a content ratio (% cation)Ratio (R)²⁺/Al³⁺) Preferably 1.50 or more and 4.00 or less.

In particular, by making the ratio (R)²⁺/Al³⁺) At 1.50 or more, the maximum value of the linear expansion coefficient can be reduced, and the refractive index of the glass can be increased. Thus, the (R) is²⁺/Al³⁺) The lower limit of the ratio is preferably 1.50 or more, more preferably 1.80 or more, still more preferably 2.10 or more, and further preferably 2.40 or more.

On the other hand, by making the ratio (R)²⁺/Al³⁺) At 4.00 or less, the linear expansion coefficient can be reduced, the refractive index can be suppressed from rising more than necessary, and the abbe number can be increased. Thus, the (R) is²⁺/Al³⁺) The upper limit of the ratio is preferably 4.00 or less, more preferably 3.80 or less, further preferably 3.70 or less, still further preferably 3.50 or less, and further preferably 3.30 or less.

In addition, an optical glass of the present invention, Ba²⁺Content ratio (% cation) and Al³⁺Ratio of content (cation%) (Ba²⁺/Al³⁺) Preferably 2.50 or less. By reducing the ratio (Ba)²⁺/Al³⁺) The refractive index can be suppressed from increasing more than necessary while suppressing a decrease in resistance to devitrification. Thus, the (Ba)²⁺/Al³⁺) The upper limit of the ratio is preferably 2.50 or less, more preferably 2.00 or less, further preferably 1.80 or less, still further preferably 1.50 or less, and further preferably 1.30 or less.

On the other hand, (Ba)²⁺/Al³⁺) The lower limit of the ratio is preferably greater than 0, more preferably greater than 0.20, and still more preferably greater than 0.40.

In addition, an optical glass of the present invention, Ba²⁺Content ratio (% cation) and Mg²⁺Ratio of content (cation%) (Ba²⁺/Mg²⁺) Preferably 5.00 or less. This makes it possible to obtain glass having high devitrification resistance. Thus, the (Ba)²⁺/Mg²⁺) The upper limit of the ratio is preferably 5.00 or less, more preferably 4.50 or less, still more preferably 4.00 or less, further preferably 3.80 or less, further preferably 3.50 or less, and still further more preferably3.20 or less, and more preferably 3.00 or less.

In addition, (Ba)²⁺/Mg²⁺) The lower limit of the ratio is preferably greater than 0, more preferably 0.50 or more, further preferably 0.70 or more, and still further preferably 0.90 or more.

Ln³⁺Is referred to as from La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺1 or more selected from the group consisting of. Additionally, Ln³⁺The total content of (A) is La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺A total of 1 or more selected from the group consisting of.

Here, by mixing Ln³⁺The total content of (3) is reduced to 13.0% or less, and the glass can be made difficult to devitrify. Thus, Ln³⁺The upper limit of the total content of (b) is preferably 13.0%, more preferably 10.0% or less, still more preferably 7.0% or less, still more preferably 4.0% or less, and still more preferably 3.0% or less.

Ln, on the other hand³⁺The lower limit of the total content of (b) is preferably more than 0%, more preferably 0.3% or more, and still more preferably 0.5% or more, from the viewpoint of further improving the refractive index and the abbe number.

Rn⁺Is derived from Li⁺、Na⁺And K⁺More than 1 kind is selected from the group. In addition, Rn⁺The total content of (A) is derived from Li⁺、Na⁺And K⁺Selecting a total of 1 or more from the group.

Here, by mixing Rn⁺The total content of (3) is reduced to 10.0% or less, and the degree of abrasion of the glass can be reduced, thereby improving chemical durability. Thus, Rn⁺The upper limit of the total content of (b) is preferably 10.0%, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 1.0% or less, and still more preferably 0.3% or less.

Optical glass of the invention, P⁵⁺、Si⁴⁺And B³⁺Is composed ofThe total ratio (% cation) is preferably 17.0% or more and 42.0% or less.

Here, by making P⁵⁺、Si⁴⁺And B³⁺The total content of (2) is 17.0% or more, and the refractive index of the glass can be increased. Therefore, the sum of their contents (P)⁵⁺+Si⁴⁺+B³⁺) The lower limit of (b) is preferably 17.0% or more, more preferably 20.0% or more, still more preferably 23.0% or more, and further preferably 26.0% or more.

In addition, by making P⁵⁺、Si⁴⁺And B³⁺The total content of (3) is 42.0% or less, and the Abbe number of the glass can be increased. Therefore, the sum of their contents (P)⁵⁺+Si⁴⁺+B³⁺) The upper limit of (b) is preferably 42.0% or less, more preferably 40.0% or less, still more preferably 37.0% or less, and further preferably 33.0% or less.

Optical glass of the invention, F^－Content ratio (% anion) and P⁵⁺Ratio of content (cation%) (F)^－/P⁵⁺) Preferably 0.80 or more. By increasing the ratio (F)^－/P⁵⁺) The Abbe number of the glass can be increased. Thus, the (F)^－/P⁵⁺) The lower limit of the ratio is preferably 0.80 or more, more preferably 0.90 or more, and still more preferably 1.00 or more.

On the other hand, (F)^－/P⁵⁺) The upper limit of the ratio is preferably 3.00 or less, more preferably 2.50 or less, still more preferably 2.20 or less, further preferably 2.05 or less, and further preferably 1.95 or less, from the viewpoint of reducing the linear expansion coefficient and reducing the devitrification of the glass.

Optical glass of the present invention, Ba²⁺Content ratio of (cation%) and F^－Total content of (5) (anion%) (Ba)²⁺+F^－) Preferably 87.0% or less. This reduces devitrification of the glass, increases the partial dispersion ratio (θ g, F), and reduces the maximum value of the linear expansion coefficient. Thus, Ba²⁺Content ratio of (A) and (F)^－The sum of the contents of (Ba)²⁺+F^－) The upper limit thereof is preferably 87.0% or moreThe content is more preferably 85.0% or less, still more preferably 82.0% or less, still more preferably 80.0% or less, and still more preferably 77.7% or less.

In addition, Ba²⁺Content ratio of (A) and (F)^－The sum of the contents of (Ba)²⁺+F^－) The lower limit of (b) is preferably 37.0% or more, more preferably 40.0% or more, still more preferably 45.0% or more, still more preferably 47.0% or more, and still more preferably 50.0% or more.

Optical glass of the invention, F^－The ratio (F) of the content (anion%) of (a) to the partial dispersion ratio (θ g, F)^－/(θ g, F)), preferably 105 or less. To increase the partial dispersion ratio (. theta.g, F), F is increased^－The content of (B) is effective, but if F^－When the content of (B) is increased, F is added to the glass in a thin plate state in press molding of a large amount^－The volatilization of (2) causes fine pores to be formed on the surface, resulting in a fogged state. Thus, the ratio (F)^－/(θ g, F)) is preferably 105 or less, more preferably 100 or less, still more preferably 98 or less, and most preferably 95 or less.

[ other Components ]

The optical glass of the present invention may contain other components as needed within a range that does not impair the characteristics of the glass of the present invention.

[ regarding components that should not be contained ]

Next, components that should not be contained in the optical glass of the present invention, and preferably not contained therein, will be described.

In addition to Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, various transition metal components such as Cu, Nd, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo are contained alone or in a composite form, and therefore, the glass is colored even if contained in a small amount and absorbs light having a specific wavelength in the visible light region, and therefore, it is preferable that the glass is substantially not contained in optical glass using a wavelength in the visible light region.

Cations of Pb, As, Th, Cd, Tl, Os, Be and Se have recently been used As harmful chemical substancesHowever, the use of the glass is avoided, and environmental measures are required not only in the glass production step but also in the processing step and the disposal after the product formation. In addition, S (sulfur) cations also produce harmful chemicals (SO)_xEtc.). Therefore, when importance is attached to the environmental influence, the content of 1 or more species therein is preferably less than 1.0%, more preferably less than 0.5%, and most preferably 1 or more species therein is not substantially contained.

In the present specification, "substantially not containing" means that the content is preferably less than 0.1%, and more preferably not containing except inevitable impurities.

Cations of Sb and Ce can be used as an antifoaming agent, but these cations tend not to be included in optical glass in recent years as environmentally undesirable components. Therefore, in the optical glass of the present invention, it is preferable that Sb or Ce is not substantially contained from this point of view.

[ method for producing optical glass ]

The method for producing the optical glass of the present invention is not particularly limited. For example, the raw materials are uniformly mixed so that the contents of the respective components are within a predetermined range, the mixture thus prepared is put into a quartz crucible, an alumina crucible, or a platinum crucible to be roughly melted, then put into a platinum crucible, a platinum alloy crucible, or an iridium crucible to be melted at a temperature within a range of 900 to 1200 ℃ for 2 to 10 hours, stirred to be homogenized and defoamed, and then, the temperature is lowered to 850 ℃ or lower to be finely stirred to remove the texture, and the mixture is cast into a mold and slowly cooled, thereby producing the ceramic.

[ Properties ]

The optical glass of the present invention has a high refractive index (n)_d) And has low dispersibility (high abbe number).

The optical glass of the present invention has a refractive index (n)_d) Preferably 1.48000 or more and 1.58000 or less. More specifically, the lower limit of the refractive index of the optical glass of the present invention is preferably 1.48000 or more, more preferably 1.50000 or more, and further preferably 1.52000 or more. In another aspect, the optical glass of the present invention, refractionRate (n)_d) The upper limit of (b) is preferably 1.58000 or less, more preferably 1.56000 or less, and further preferably 1.54000 or less.

The optical glass of the present invention has an Abbe's number (. nu.) of_d) Preferably 68.00 or more and 88.00 or less. More specifically, the optical glass of the present invention has an Abbe's number (. nu.) of_d) The lower limit of (b) is preferably 68.00 or more, more preferably 70.00 or more, and still more preferably 75.00 or more. On the other hand, the optical glass of the present invention has an Abbe's number (. nu.) of_d) The upper limit of (b) is preferably 88.00 or less, more preferably 85.00 or less, still more preferably 82.00 or less, and further preferably 79.00 or less.

By having such a high refractive index, a large amount of light refraction can be obtained even when the optical element is thinned. Further, by having such low dispersion, when used as a single lens, the shift of the focal point (chromatic aberration) due to the wavelength of light can be reduced. Therefore, for example, when the optical system is configured by combining an optical element having high dispersion (low abbe number), the aberration of the entire optical system can be reduced, and high imaging characteristics can be realized.

As described above, the optical glass of the present invention can exhibit an effect in optical design, and particularly, when an optical system is configured, it is possible to achieve not only high imaging characteristics but also downsizing of the optical system, and it is possible to improve the degree of freedom in optical design.

The optical glass of the present invention has a high partial dispersion ratio (θ g, F).

More specifically, the partial dispersion ratio (θ g, F) of the optical glass of the present invention is not particularly limited, but is preferably 0.5650 or less, more preferably 0.5645 or less. On the other hand, the lower limit of the partial dispersion ratio (θ g, F) of the optical glass of the present invention is preferably 0.5290 or more, more preferably 0.5295 or more, and still more preferably 0.5300 or more. In addition, the optical glass of the present invention has a partial dispersion ratio (θ g, F) and an Abbe number (v)_d) Preferably satisfies the relationship (1) (0.0069 x ν)_d+0.980)≤(θg，F)≤(－0.0069×ν_d+ 1.105).

Thus, the optical glass of the present invention has a higher partial dispersion ratio (θ g, F) than the conventionally known fluorophosphate glasses. Therefore, an optical element formed of the optical glass can be suitably used for correction of chromatic aberration.

Here, the Abbe number (. nu.) of the optical glass of the present invention_d) The lower limit of the partial dispersion ratio (θ g, F) is not particularly limited, but it is preferably (-0.0069 × ν)_d+0.980), more preferably (-0.0069 x ν)_d+0.990) or more, and still more preferably (-0.0069 x ν_d+1.000) or more. On the other hand, the Abbe number (. nu.) of the optical glass of the present invention_d) The upper limit of the partial dispersion ratio (. theta.g, F) is preferably (-0.0069X v)_d+1.105), more preferably (-0.0069 x ν_d+1.095) or less, and still more preferably (-0.0069 x ν_d+1.085) or less.

In the optical glass of the present invention, the maximum value (α) of the linear expansion coefficient in the temperature range between the glass transition point (Tg) and the sag point (At)_max) Preferably at 1300X 10^－7K^－1The following. Thus, even when a thin optical element is manufactured, the glass is less likely to break when heated to a temperature higher than the glass transition point and press-molded, and therefore, the productivity of the optical element can be improved. As a reason why such glass is hard to break, for example, when the glass is heated and softened and when the softened glass is press-molded and cooled, a high temperature portion at a glass transition point or higher where the linear expansion coefficient is large and a low temperature portion at a glass transition point or lower where the linear expansion coefficient is small can be defined in the glass based on the temperature difference in the glass, and at this time, the thermal expansion and thermal contraction of the high temperature portion become small, and therefore, the force applied to the low temperature portion by the thermal expansion and thermal contraction of the high temperature portion becomes small.

Therefore, in the optical glass of the present invention, the maximum value (α) of the linear expansion coefficient in the temperature range between the glass transition point (Tg) and the sag point (At)_max) The upper limit of (2) is preferably 1300X 10^－7K^－1More preferably 1250X 10^－7K^－1Hereinafter, the following are still more preferred1200×10^－7K^－1More preferably 1150 × 10^－7K^－1Still more preferably 1100 × 10^－7K^－1More preferably, the average particle size is 1000X 10^－7K^－1The most preferable range is 950X 10^－7K^－1The following.

In the present specification, the maximum value of the linear expansion coefficient in the temperature range between the glass transition point (Tg) and the sag point (At) may be simply referred to as "the maximum value of the linear expansion coefficient".

The optical glass of the present invention preferably has a small average linear expansion coefficient (. alpha.). Particularly, the optical glass of the present invention preferably has an average linear expansion coefficient α of 100 to 300 ℃ as defined in Japanese optical glass Industrial Association Standard JOGIS 08-2003, and an upper limit thereof is 160X 10^－7℃^－1More preferably 155X 10 or less^－7℃^－1Hereinafter, it is still more preferably 150X 10^－7℃^－1The following. Thus, even if press molding is performed, the problems due to temperature changes and the like can be reduced, and thus an optical element such as a lens can be stably manufactured.

The lower limit of the average linear expansion coefficient (α) of the optical glass of the present invention is not particularly limited, but the lower limit of the average linear expansion coefficient (α) of the optical glass of the present invention is, for example, 90 × 10^－7℃^－1Above, 100 × 10^－7℃^－1Above or 110 × 10^－7℃^－1The above.

The optical glass of the present invention has a maximum value of linear expansion coefficient (. alpha.)_max) Ratio of coefficient of linear expansion (alpha) (. alpha.) (alpha.)_max) /(. alpha.)) is preferably in the range of 5.80 to 8.00. Although F is increased in order to decrease the maximum value of the linear expansion coefficient^－The content of (B) is effective, but when F is present^－When the content of (A) is increased, not only the linear expansion coefficient is increased, but also F is increased when a large amount of glass in a thin plate state is press-molded^－The volatilization of (2) causes fine pores to be formed on the surface, and the surface becomes a fogged state. Thus, the ratio (. alpha.) is_max)/(α)) The upper limit of (b) is preferably 8.00 or less, more preferably 7.60 or less, still more preferably 7.55 or less, and most preferably 7.50 or less.

On the other hand, the ratio (. alpha.) is_max) The lower limit of/(. alpha.)) is preferably 5.80 or more, more preferably 5.85 or more, still more preferably 5.90 or more, and most preferably 5.95 or more.

The optical glass of the present invention preferably has a glass transition point (Tg) of 550 ℃ or lower. Thereby, the glass is softened at a lower temperature, and thus the glass can be press-molded at a lower temperature. Further, oxidation of the mold used for press molding can be reduced, and the life of the mold can be prolonged. Therefore, the upper limit of the glass transition point of the optical glass of the present invention is preferably 550 ℃ or lower, more preferably 530 ℃ or lower, and still more preferably 510 ℃ or lower. The lower limit of the glass transition point of the optical glass of the present invention is not particularly limited, but the lower limit of the glass transition point of the optical glass of the present invention is preferably 100 ℃ or higher, more preferably 200 ℃ or higher, and still more preferably 300 ℃ or higher.

The optical glass of the present invention preferably has a sag point (At) of 595 ℃ or lower. The yield point is one of the indexes indicating the softening property of the glass, and is an index indicating a temperature close to the press molding temperature, similarly to the glass transition point. Therefore, by using a glass having a yield point of 595 ℃ or lower, press molding at a lower temperature can be realized, and press molding can be performed more easily. Therefore, the optical glass of the present invention has a sag point of preferably 595 ℃ or lower, more preferably 575 ℃ or lower, still more preferably 555 ℃ or lower, and most preferably 530 ℃ or lower. The lower limit of the sag point of the optical glass of the present invention is preferably 150 ℃ or higher, more preferably 250 ℃ or higher, and still more preferably 350 ℃ or higher.

In the optical glass of the present invention, the difference between the glass transition point (Tg) and the yield point (At) is preferably 45 ℃ or less. If the difference between the glass transition point and the yield point is small, the glass is likely to be rapidly solidified during press molding and cooling, and therefore, the adhesion of the glass to the press mold can be reduced. Therefore, the difference between the glass transition point (Tg) and the yield point (At) in the present invention is preferably 45 ℃ or lower, more preferably 43 ℃ or lower, still more preferably 40 ℃ or lower, and still more preferably 38 ℃ or lower.

[ thin sheet working ]

The optical glass of the present invention is preferably processed into a thin plate because precision molding is assumed to be performed in a thin plate state. By making the thickness of the sheet to be 0.2 to 10.0 mm, the target lens thickness can be obtained and can be suitably used. The thickness of the thin plate is preferably 0.2 to 10.0 mm, more preferably 0.4 to 6.0 mm, and most preferably 0.6 to 3.0 mm. The method for processing the optical glass into a sheet is not particularly limited, and examples thereof include a method for grinding and polishing the surface of the glass to form a sheet, a known downflow method (downflow), and the like.

[ volatility ]

The optical glass of the present invention is supposed to be formed by pressing a large amount of thin plates. Thus, in the above-mentioned press molding, F^－The smaller the amount of volatile components to be volatilized is, the more preferable. Specifically, when the press molding is performed at 450 to 650 ℃, it is preferable that the glass surface does not generate fogging due to volatilization. The temperature of the pressure forming is preferably 450 to 650 ℃, more preferably 480 to 630 ℃, and further preferably 520 to 610 ℃.

[ preform and optical element ]

The method for molding the glass of the present invention into an optical element is not particularly limited, and is particularly suitable for producing a spherical or aspherical lens by precision press molding.

For example, a spherical or aspherical lens can be produced by a method of heating and softening a preform material obtained by cutting and polishing a glass gob or a glass block, and pressure-molding the preform using a molding die having a highly precise surface to produce a preform, and precision press-molding the preform.

Further, the optical glass of the present invention has a characteristic that the maximum value of the linear expansion coefficient is small, and therefore, a thin plate whose surface has been finished to a mirror surface can be manufactured, and a plurality of optical elements can be manufactured at one time by pressing the thin plate using a mold having a plurality of molding surfaces.

The glass molded body made of the optical glass of the present invention can be used for applications of optical elements such as lenses, prisms, and mirrors, and can be typically used for devices requiring thin and light lenses such as lenses for mobile phones and lenses for smart phones.

Examples

The optical glasses of examples 1 to 7 and comparative examples 1 to 4 of the present invention had compositions (in terms of mole% expressed as cation% or anion%) and refractive indices (n)_d) Abbe number (v)_d) Partial dispersion ratio (. theta.g, F), glass transition point (Tg), glass yield point (At), and large value of linear expansion coefficient (. alpha.)_max) The results of (a) are shown in tables 1 and 2. It should be noted that the following embodiments are merely examples and are not limited to these embodiments.

In each of examples and comparative examples, high-purity raw materials used for general fluorophosphate glasses such as various corresponding oxides, carbonates, nitrates, fluorides, metaphosphate compounds, and the like were selected as raw materials of each component, weighed to obtain the compositions of each example shown in the table, uniformly mixed, placed in a platinum crucible and covered with a lid, heated at 950 to 1100 ℃ for 2 hours using an electric furnace, stirred while melting the raw materials to homogenize and defoam, and then, the temperature was lowered to 850 ℃ or lower, cast into a mold, and slowly cooled to produce glass.

Refractive index (n) of glasses of examples and comparative examples_d) Abbe number (v)_d) And a partial dispersion ratio (θ g, F) in accordance with JIS B7071-2: 2018 by the V-Block method. Here, the refractive index (n)_d) This is expressed as a measurement on the d-line (587.56nm) of the helium lamp. In addition, Abbe number (. nu.)_d) Using refractive index (n) to the d-line of a helium lamp_d) Refractive index (n) of F-line (486.13nm) of hydrogen lamp_F) Refractive index (n) to C line (656.27nm)_C) According to Abbe number (v)_d)＝[(n_d－1)/(n_F－n_C)]The equation (2) is calculated. In addition, partial dispersionThe refractive index (ng) for g-line of Hg lamp and the refractive index (n) for F-line (486.13nm) of hydrogen lamp were used as the ratio (θ g, F)_F) Refractive index (n) to C line (656.27nm)_C) According to the partial dispersion ratio (θ g, F) ═ ng-n_F)/(n_F－n_C) Is calculated by the following equation. These refractive indices (n)_d) Abbe number (v)_d) And the partial dispersion ratio (. theta.g, F) were measured for a glass having a slow cooling rate of-25 ℃/hr.

And, based on the Abbe number (. nu.) obtained by the measurement_d) And the values of the partial dispersion ratios (theta g, F), and obtaining a relation (theta g, F) — a₂×ν_d+b₂A slope of₂Intercept b at 0.0069₂。

The glass transition point (Tg) and the yield point (At) of the glasses of examples and comparative examples were determined from thermal expansion curves obtained by measuring the relationship between the temperature and the elongation of the sample in accordance with "method for measuring thermal expansion of optical glass" standard by japan optical glass industry association, japan 08-2019.

In addition, the maximum value of the linear expansion coefficient (α) of the glasses of examples and comparative examples_max) The maximum value of the linear expansion coefficient on a scale of 5 ℃ from the glass transition point (Tg) to the yield point (At) was determined by forming a round rod having a sample length of 20. + -. 1.0mm or more and a diameter of 4. + -. 1.0mm and measuring the round rod in accordance with "method for measuring thermal expansion of optical glass" of Japan optical glass Industrial Standard JOGIS 08-2019. The linear expansion coefficient was calculated using the length of the sample at a temperature of 5 times.

[ TABLE 1 ]

[ TABLE 2 ]

As shown in the table, the refractive index (n) of the optical glass of the examples of the present invention_d) Both are 1.48000 or more, more specifically 1.52000 or more, within the desired range. The optical glasses according to examples of the present invention all had abbe numbers of 68.00 or more, which were within the desired ranges.

In addition, the optical glasses of the examples of the present invention have all of the partial dispersion ratios (θ g, F) of 0.5290 or more, and F^－The ratio (F) of the content (anion%) of (a) to the partial dispersion ratio (θ g, F)^－And/(. theta.g, F)) is 105 or less. As shown in FIGS. 1 and 2, the glass of example 2 had no F formed on the surface thereof^－Fogging due to volatilization of (2) produced F in the glass of comparative example 3^－Is used for the formation of a mist.

In addition, the optical glass of the examples of the present invention has a maximum value (α) of the linear expansion coefficient in the temperature range between the glass transition point (Tg) and the sag point (At)_max) Are all 1300 x 10^－7K^－1The following ranges are within the desired range.

In addition, the optical glasses according to the examples of the present invention all had a glass transition point (Tg) of 550 ℃ or lower within a desired range.

In the optical glasses of examples of the present invention, the glass yield point (At) was 595 ℃ or lower, and was within a desired range.

In addition, the optical glasses according to examples of the present invention had a difference between the glass transition point (Tg) and the glass yield point (At) of 45 ℃ or less, which was within a desired range.

Therefore, it is understood that the optical glass of the examples of the present invention has a refractive index and Abbe number within a desired range, a large partial dispersion ratio (. theta.g, F), and a maximum value (. alpha.) of the linear expansion coefficient_max) And the average linear expansion coefficient (α) is small. From this fact, it is presumed that the optical glass according to the embodiment of the present invention can reduce the breakage and crack of the glass, and can stably obtain the glass.

Although the present invention has been described in detail for the purpose of illustration, the present embodiment is for illustrative purposes only, and it is to be fully understood that many modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A fluorophosphate optical glass for sheet molding, in which,

expressed as cationic% (mol%):

P⁵⁺at least 17.0% and at most 42.0%,

from La³⁺、Gd³⁺、Y³⁺、Yb³⁺And Lu³⁺A total content Ln of 1 or more selected from the group³⁺(cation%) is 13.0% or less,

expressed as anionic% (mol%):

F^－the content of (A) is 30.0 to 60.0%;

refractive index (n)_d) Above 1.48000 and below 1.58000,

abbe number (v)_d) In the range of 68.00 or more and 88.00 or less,

a partial dispersion ratio (θ g, F) of 0.5290 or more,

F^－the ratio (F) of the content (anion%) of (a) to the partial dispersion ratio (θ g, F)^－/(. theta.g, F)) is 105 or less,

maximum value of linear expansion coefficient (. alpha.)_max) Is 1300 x 10^－7K^－1The following.

2. The optical glass as claimed in claim 1, wherein Ca²⁺Content ratio (% cation) and R²⁺(cation%) ratio (Ca)²⁺/R²⁺) Above 0.18.

3. The optical glass according to claim 1 or 2, wherein the difference between the glass transition point (Tg) and the yield point (At) is 45 ℃ or less.

4. A fluorophosphoric acid optical glass for large-amount press, wherein,

expressed as cationic% (mol%):

P⁵⁺at least 17.0% and at most 42.0%,

expressed as anionic% (mol%):

F^－the content of (A) is 30.0 to 60.0%;

refractive index (n)_d) Above 1.48000 and below 1.58000,

abbe number (v)_d) In the range of 68.00 or more and 88.00 or less,

a partial dispersion ratio (θ g, F) of 0.5290 or more,

5. The fluorophosphoric acid optical glass according to claim 4, wherein Ca²⁺Content ratio (% cation) and R²⁺(cation%) ratio (Ca)²⁺/R²⁺) Above 0.18.

6. The fluorophosphate optical glass according to claim 4 or 5, wherein the difference between the glass transition point (Tg) and the yield point (At) is 45 ℃ or less.

7. An optical element made of the glass as defined in any one of claims 1 to 6.

8. A preform for polishing and/or precision press molding made of the glass according to any one of claims 1 to 6.

9. A lens made of the optical element according to claim 7.