JP2017031054A - Optical glass, preform and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass preferably used for correction of color aberration while having refraction index (n) and Abbe number (ν) in desired ranges and a lens preform using the same.SOLUTION: An optical glass contains a BOcomponent and a LaOcomponent and has refraction index (n) of 1.73 or more and Abbe number (ν) of 45 or more and satisfies a relationship of (θg,F)≥(-0.00170×ν+0.63750) between partial dispersion ratio (θg,F) and Abbe number (ν).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical glass, a preform, and an optical element.

  Optical systems such as digital cameras and video cameras, although large and small, contain blurs called aberrations. This aberration is classified into monochromatic aberration and chromatic aberration. In particular, the chromatic aberration is strongly dependent on the material characteristics of the lens used in the optical system.

  In general, chromatic aberration is corrected by combining a low-dispersion convex lens and a high-dispersion concave lens. However, this combination can only correct aberrations in the red region and the green region, and remains in the blue region. This blue region aberration that cannot be removed is called a secondary spectrum. In order to correct the secondary spectrum, it is necessary to perform an optical design in consideration of the trend of the g-line (435.835 nm) in the blue region. At this time, the partial dispersion ratio (θg, F) is used as an index of the optical characteristics to be noticed in the optical design. In the optical system combining the low dispersion lens and the high dispersion lens, an optical material having a large partial dispersion ratio (θg, F) is used for the low dispersion side lens, and the partial dispersion ratio ( By using an optical material having a small θg, F), the secondary spectrum is corrected well.

The partial dispersion ratio (θg, F) is expressed by the following equation (1).
θg, F = (n _g −n _F ) / (n _F −n _C ) (1)

In optical glass, there is an approximately linear relationship between a partial dispersion ratio (θg, F) representing partial dispersion in a short wavelength region and an Abbe number (ν _d ). The straight line representing this relationship plots the partial dispersion ratio and Abbe number of NSL7 and PBM2 on the Cartesian coordinates employing the partial dispersion ratio (θg, F) on the vertical axis and the Abbe number (ν _d ) on the horizontal axis. It is represented by a straight line connecting two points and is called a normal line (see FIG. 1). Normal glass, which is the standard for normal lines, differs depending on the optical glass manufacturer, but each company defines it with almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by OHARA, Inc., and the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θg, F) is 0.5828, and the Abbe number (ν _d ) of NSL7. Is 60.5, and the partial dispersion ratio (θg, F) is 0.5436.)

Here, as a glass having a high refractive index (n _d ) of 1.73 or more and a high Abbe number (low dispersion) of 45 or more, for example, optical glasses as shown in Patent Documents 1 to 3 are known. ing.

JP 2007-261877 A JP 2009-084059 A JP 2009-242210 A

  However, the optical glasses of Patent Documents 1 to 3 do not have a large partial dispersion ratio and are not sufficient for use as a lens for correcting the secondary spectrum. That is, an optical glass having a low dispersion and a large partial dispersion ratio (θg, F) is required.

The present invention has been made in view of the above problems, and its object is to correct chromatic aberration while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. The object is to obtain a preferably used optical glass and a lens preform using the same.

In order to solve the above-mentioned problems, the present inventors have conducted extensive test studies. As a result, the B ₂ O ₃ component and the La ₂ O ₃ component are used in combination to achieve high refractive index and low dispersion of the glass. However, the present inventors have found that the partial dispersion ratio (θg, F) of the glass has a desired relationship with the Abbe number (ν _d ), thereby completing the present invention. Specifically, the present invention provides the following.

(1) It contains a B ₂ O ₃ component and a La ₂ O ₃ component, has a refractive index (n _d ) of 1.73 or more, an Abbe number (ν _d ) of 45 or more, and a partial dispersion ratio (θg , F) satisfies the relationship (θg, F) ≧ (−0.00170 × ν _d +0.63750) with the Abbe number (ν _d ).

(2) the entire mass of the glass in terms of oxide composition, 5.0 to 50.0% of _B 2 _{O 3} component in mass%, _La 2 _{O 3} content of the component from 10.0 to 55.0% The optical glass described in (1).

  (3) The optical glass according to (1) or (2), wherein the content of the F component is 30.0% or less in an externally divided mass% with respect to the oxide-based mass.

(4) Bi ₂ O ₃ component 0 to 10.0% and / or TiO ₂ component 0 to 15.0% and / or WO ₃ component 0 to 15% by mass with respect to the total glass mass of the oxide equivalent composition 0.0% and / or Nb ₂ O ₅ component 0-20.0% and / or K ₂ O component 0-10.0%
The optical glass according to any one of (1) to (3), further comprising:

(5) The optical glass according to (4), wherein the mass sum (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) with respect to the total glass mass of the oxide equivalent composition is 1.0% or more.

(6) 0 to 15.0% of Ta ₂ O ₅ component and / or ZrO ₂ component 0 to 15.0% and / or Li ₂ O component 0 to ₅ % by mass with respect to the total glass mass of the oxide conversion composition 5.0%
The optical glass according to any one of (1) to (5).

(7) The mass ratio (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) / (Ta ₂ O ₅ + ZrO ₂ + Li ₂ O) of the oxide equivalent composition is 1.3 or more (6) Optical glass.

(8) Gd ₂ O ₃ component 0 to 40.0% and / or Y ₂ O ₃ component 0 to 20.0% and / or Yb ₂ O _{3 in} mass% with respect to the total glass mass of the oxide equivalent composition. components from 0 to 20.0% and / or _Lu 2 _{O 3} component from 0 to 20.0%
The optical glass according to any one of (1) to (7), further containing each component of:

(9) The optical glass according to any one of (1) to (8), wherein the content of Gd ₂ O ₃ is 29.5% or less by mass with respect to the total glass mass of the oxide equivalent composition.

(10) The mass sum of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) with respect to the total glass mass of the oxide equivalent composition is 43.0. The optical glass according to any one of (1) to (9), which is more than% and not more than 80.0%.

(11) 0 to 10.0% of MgO component and / or 0 to 15.0% of CaO component and / or 0 to 15.0% of SrO component and / Or BaO component 0-25.0%
The optical glass according to any one of (1) to (10), further containing each component of

  (12) The mass sum of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) with respect to the total glass mass of the oxide equivalent composition is 20.0% or less ( 11) The optical glass as described.

(13) The optical glass according to any one of (1) to (12), wherein the content of the SiO ₂ component is 25.0% or less by mass with respect to the total glass mass of the oxide equivalent composition.

  (14) The optical glass according to any one of (1) to (13), in which the content of the ZnO component is 15.0% or less by mass with respect to the total glass mass of the oxide equivalent composition.

(15) GeO ₂ component 0 to 10.0% and / or P ₂ O ₅ component 0 to 10.0% and / or Al ₂ O ₃ component in mass% with respect to the total mass of the glass in oxide equivalent composition 0 10.0% and / or _Ga 2 _{O 3} component from 0 to 10.0% and / or Na ₂ O component from 0 to 10.0% and / or SnO ₂ component 0 to 1.0% and / or Sb ₂ O ₃ component 0 to 1.0%
The optical glass according to any one of (1) to (14), further comprising:

  (16) A preform material comprising the optical glass according to any one of (1) to (15).

  (17) An optical element produced by press-molding the preform material according to (16).

  (18) An optical element having the optical glass according to any one of (1) to (15) as a base material.

  (19) An optical apparatus comprising the optical element according to any one of (17) and (18).

According to the present invention, an optical glass that can be preferably used for correcting chromatic aberration while having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges, and a preform and an optical element using the optical glass. Can be obtained.

It is a figure which shows the normal line by which partial dispersion ratio ((theta) g, F) is represented on the orthogonal coordinate of a vertical axis | shaft and Abbe number ((nu) _d ) on a horizontal axis.

The optical glass of the present invention contains a B ₂ O ₃ component and a La ₂ O ₃ component, and has a refractive index (n _d ) of 1.73 or more and an Abbe number (ν _d ) of 45 or more. The dispersion ratio (θg, F) satisfies the relationship of (θg, F) ≧ (−0.00170 × ν _d +0.63750) with the Abbe number (ν _d ). By containing the B ₂ O ₃ component and the La ₂ O ₃ component, the refractive index of the glass is increased and the dispersion is reduced. Further, by satisfying the relationship of (θg, F) ≧ (−0.00170 × ν _d +0.63750) between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ), the optical Chromatic aberration of an optical element formed from glass is reduced. Therefore, an optical glass that can be preferably used for correcting chromatic aberration while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges, and a preform and an optical element using the optical glass are obtained. Can do.

  Hereinafter, embodiments of the optical glass of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, unless there is particular notice, content of each component shall be displayed by the mass% with respect to the glass total mass of an oxide conversion composition. Here, the “oxide equivalent composition” means that the oxide, composite salt, metal fluoride, etc. used as the raw material of the glass component of the present invention are all decomposed and changed into oxides when melted. It is the composition which described each component contained in glass by making the total mass of the said production | generation oxide into 100 mass%.

<About essential and optional components>
The B ₂ O ₃ component is a component that forms a network structure inside the glass and promotes stable glass formation. In particular, by making the content of the B ₂ O ₃ component 5.0% or more, it is difficult to devitrify the glass, and a stable glass can be easily obtained. On the other hand, by making the content of the B ₂ O ₃ component 50.0% or less, a desired refractive index and dispersibility can be easily obtained. Therefore, the content of the B ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%, more preferably 10.0%, most preferably 15.0%, and preferably 50%. The upper limit is 0.0%, more preferably 40.0%, and most preferably 35.0%. The B ₂ O ₃ component can be contained in the glass using, for example, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ .10H ₂ O, BPO ₄ or the like as a raw material.

The La ₂ O ₃ component is a component that increases the refractive index of the glass and decreases dispersion. In particular, by making the content of the La ₂ O ₃ component 10.0% or more, it is easy to obtain a glass having a desired high refractive index and a high Abbe number and a high transmittance for visible light. it can. On the other hand, by setting the content of the La ₂ O ₃ component to 55.0% or less, it is possible to suppress the phase separation of the glass and make it difficult to devitrify the glass when producing the glass. Therefore, the content of the La ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 15.0%, most preferably 20.0%, and preferably 55%. 0.0%, more preferably 52.0%, and most preferably 50.0%. The La ₂ O ₃ component can be contained in the glass using, for example, La ₂ O ₃ , La (NO ₃ ) ₃ .XH ₂ O (X is an arbitrary integer) or the like as a raw material.

F component is a component which raises the partial dispersion ratio of glass, and is a component which lowers | hangs the transition point (Tg) of glass. In particular, it is possible to make the glass difficult to devitrify by setting the content of the F component to 30.0% or less with an outer mass% based on the oxide-based mass. Therefore, the content of the F component in the outer ratio with respect to the mass based on the oxide is preferably 30.0%, more preferably 25.0%, and still more preferably 20.0%. In addition, although the optical glass of the present invention can obtain an optical glass having a desired high partial dispersion ratio without containing the F component, the high portion is obtained by containing 0.1% or more of the F component. An optical glass with little coloration can be obtained while having a dispersion ratio. Therefore, the content of the F component in an external ratio with respect to the mass based on the oxide is preferably 0.1%, more preferably 1.0%, still more preferably 5.0%, still more preferably 6.2%, More preferably, the lower limit is 6.8%. The F component can be contained in the glass using, for example, ZrF ₄ , AlF ₃ , NaF, CaF ₂ , LaF ₃ or the like as a raw material.

  Note that the content of the F component in this specification is based on the assumption that all the cation components constituting the glass are made of an oxide combined with oxygen that balances the charge, and the total mass of the glass made of these oxides. Is 100%, and the mass of the F component is expressed in mass% (externally divided mass% with respect to the oxide-based mass).

The Bi ₂ O ₃ component is a component that increases the partial dispersion ratio of the glass, is a component that increases the refractive index of the glass and lowers the glass transition point, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, it is possible to make it difficult to deteriorate the light transmittance at a visible short wavelength (500 nm or less). Therefore, the content of the Bi ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The Bi ₂ O ₃ component can be contained in the glass using, for example, Bi ₂ O ₃ as a raw material.

The TiO ₂ component is a component that increases the partial dispersion ratio of the glass, is a component that increases the refractive index and dispersion of the glass, and improves the chemical durability of the glass, and is an optional component in the optical glass of the present invention. is there. In particular, by making the content of the TiO ₂ component 15.0% or less, a desired high Abbe number can be easily obtained, and the light transmittance at a visible short wavelength (500 nm or less) can be made difficult to deteriorate. . Therefore, the content of the TiO ₂ component with respect to the total glass mass of the oxide-converted composition is preferably 15.0%, more preferably 12.0%, and most preferably 10.0%. TiO ₂ component may be contained in the glass by using as the starting material for example TiO ₂ or the like.

The WO ₃ component is a component that increases the partial dispersion ratio of the glass, is a component that increases the refractive index and dispersion of the glass, and improves the chemical durability of the glass, and is an optional component in the optical glass of the present invention. is there. In particular, by making the content of the WO ₃ component 15.0% or less, a desired high Abbe number can be easily obtained, and the light transmittance at a visible short wavelength (500 nm or less) can be made difficult to deteriorate. . Therefore, the content of the WO ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 12.0%, and most preferably 10.0%. The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

The Nb ₂ O ₅ component is a component that increases the partial dispersion ratio of the glass, is a component that increases the refractive index and dispersion of the glass, and improves the chemical durability of the glass, and is optional in the optical glass of the present invention. It is an ingredient. In particular, when the content of the Nb ₂ O ₅ component is 20.0% or less, a desired high Abbe number can be easily obtained. Therefore, the content of the Nb ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 20.0%, more preferably 15.0%, and most preferably 10.0%. The Nb ₂ O ₅ component can be contained in the glass using, for example, Nb ₂ O ₅ as a raw material.

K 2 _O component, with a component for increasing the partial dispersion ratio of glass is a component for improving the meltability of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the K ₂ O component to 10.0% or less, the refractive index of the glass is hardly lowered, the stability of the glass is increased, and devitrification and the like are hardly caused. Therefore, the content of the K ₂ O component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The K ₂ O component can be contained in the glass using, for example, K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ or the like as a raw material.

In the optical glass of the present invention, the sum of at least one content selected from the group consisting of F component, Bi ₂ O ₃ component, TiO ₂ component, WO ₃ component, Nb ₂ O ₅ component and K ₂ O component is 1.0% is preferable. By setting this sum to 1.0% or more, the partial dispersion ratio can be increased, so that a desired high partial dispersion ratio can be easily obtained. Therefore, the sum of the contents of these components with respect to the mass of the oxide equivalent composition is preferably 1.0%, more preferably 3.0%, still more preferably 5.0%, and even more preferably 6.2%. The lower limit. On the other hand, the upper limit of the sum of the contents of these components is not particularly limited as long as a stable glass can be obtained, but it is assumed that devitrification is likely to occur when, for example, it exceeds 60.0%. Therefore, the sum of the contents of these components with respect to the mass of the oxide equivalent composition is preferably 60.0%, more preferably 50.0%, and most preferably 40.0%. In addition, in the sum of this content, the content of the F component refers to the content of the external division with respect to the mass of the oxide basis, Bi ₂ O ₃ component, TiO ₂ component, WO ₃ component, Nb ₂ O ₅ component and the K 2 _O content component refers to the content of the glass the total weight of the oxide basis composition.

Among these components, the K ₂ O component has an action of lowering the refractive index. Therefore, from the viewpoint of obtaining a glass having a particularly high refractive index, the F component, Bi ₂ O ₃ component, TiO ₂ component, WO ₃ component and Nb ₂ It is preferable to contain one or more selected from the group consisting of O ₅ components. Further, since the Nb ₂ O ₅ component has a strong action to lower the Abbe number, particularly from the viewpoint of obtaining a glass having a high Abbe number, the F component, Bi ₂ O ₃ component, TiO ₂ component, WO ₃ component and K ₂ O It is preferable to contain one or more selected from the group consisting of components. In addition, since the Bi ₂ O ₃ component, the TiO ₂ component, and the WO ₃ component have a strong effect of coloring the glass, the F component, the Nb ₂ O ₅ component, and the K ₂ O component are particularly preferable from the viewpoint of obtaining a glass with less coloration. It is preferable to contain 1 or more types selected from the group which consists of. Therefore, it is preferable to increase the content of the F component among these components from the viewpoint of obtaining a glass having a high partial dispersion ratio and a high refractive index and Abbe number and low coloring.

The Ta ₂ O ₅ component is a component that stabilizes the glass while increasing the refractive index of the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of the Ta ₂ O ₅ component 15.0% or less, it is possible to suppress a decrease in the partial dispersion ratio of the glass. Further, by setting the content of Ta ₂ O ₅ component below 15.0%, while reducing the material cost of the glass, it is possible to reduce the energy loss during the glass production to avoid dissolution at a high temperature . Therefore, the content of the Ta ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 5.0%. The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

ZrO ₂ component increases the refractive index of the glass is a component to improve the devitrification resistance of making the glass, are optional components in the optical glass of the present invention. In particular, by setting the content of the ZrO ₂ component to 15.0% or less, it is possible to suppress a decrease in the partial dispersion ratio of the glass. In addition, by reducing the ZrO ₂ component content to 15.0% or less, it is possible to suppress the glass Abbe number from being lowered, avoid melting at a high temperature during glass production, and reduce energy loss during glass production. can do. Therefore, the content of the ZrO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, still more preferably 5.0%, and most preferably 4.%. Less than 0%. The ZrO ₂ component can be contained in the glass using, for example, ZrO ₂ , ZrF ₄ or the like as a raw material.

Li 2 _O component is a component for improving the meltability of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the Li ₂ O component to 5.0% or less, a decrease in the partial dispersion ratio of the glass can be suppressed. Further, by the content of Li 2 _O component below 5.0%, while reduction in the refractive index of the glass, it is possible to hardly occurs devitrification etc. due to excessive content of Li 2 _O component. Therefore, the content of the Li ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%, more preferably 4.0%, still more preferably 3.0%, and even more preferably 2.3%. Is the upper limit. The Li ₂ O component can be contained in the glass using, for example, Li ₂ CO ₃ , LiNO ₃ , LiF or the like as a raw material.

In the optical glass of the present invention, the mass sum of (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) with respect to the mass sum of (Ta ₂ O ₅ + ZrO ₂ + Li ₂ O) is 1.3 or more. Is preferred. Thereby, since the content of the component which raises the partial dispersion ratio increases with respect to the content of the component which greatly reduces the partial dispersion ratio, a desired high partial dispersion ratio can be easily obtained even if more rare earths are added. That is, it is possible to easily achieve both a high partial dispersion ratio and a high Abbe number. Therefore, the mass ratio (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) / (Ta ₂ O ₅ + ZrO ₂ + Li ₂ O) in the oxide equivalent composition is preferably 1.3, more preferably 1 .5, most preferably 2.0 is the lower limit. On the other hand, the ratio of the content is not particularly limited, and may be infinite (that is, Ta ₂ O ₅ + ZrO ₂ + Li ₂ O = 0%). However, from the viewpoint of further improving the stability of the glass, this ratio May be 100.0 or less.

The Gd ₂ O ₃ component is a component that increases the refractive index of the glass and decreases the dispersion. In particular, by setting the content of the Gd ₂ O ₃ component to 40.0% or less, it is possible to suppress the phase separation of the glass and to make the glass difficult to devitrify when producing the glass. Therefore, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 40.0%, more preferably 35.0%, and most preferably 29.5%. Although it is possible to obtain a glass having a desired high partial dispersion ratio without containing a Gd ₂ O ₃ component, it is possible to obtain a desired refractive index by containing 1.0% or more of the Gd ₂ O ₃ component. And dispersibility can be made easy to obtain. Therefore, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 5.0%, and most preferably 7.0%. The Gd ₂ O ₃ component can be contained in the glass using, for example, Gd ₂ O ₃ , GdF ₃ or the like as a raw material.

The Y ₂ O ₃ component, the Yb ₂ O ₃ component, and the Lu ₂ O ₃ component are components that increase the refractive index of the glass and reduce the dispersion. _Here, by Y 2 _{O 3} component, the content of _Yb 2 _{O 3} component or _Lu 2 _{O 3} component below 20.0%, it is possible to make it difficult the glass devitrified. In particular, by making the content of the Yb ₂ O ₃ component 10.0% or less, absorption is less likely to occur on the long wavelength side of the glass (near the wavelength of 1000 nm), so that the glass can be improved in resistance to infrared rays. . Therefore, the Y ₂ O ₃ component, the Yb ₂ O ₃ component, and the Lu ₂ O ₃ component are preferably 20.0%, more preferably 15.0%, and still more preferably 10.2% with respect to the total glass mass of the oxide equivalent composition. The upper limit is 0%, and most preferably 8.0%. The Y ₂ O ₃ component, the Yb ₂ O ₃ component, and the Lu ₂ O ₃ component may be contained in the glass using, for example, Y ₂ O ₃ , YF ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ or the like as a raw material. it can.

In the optical glass of the present invention, the mass sum of the content of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 43.0%. More preferably, it is 80.0% or less. Here, by making this mass sum more than 43.0%, a desired high refractive index and Abbe number can be easily obtained, and the photoelastic constant can be reduced. In particular, in the optical glass of the present invention, even if a large amount of rare earth is contained, the partial dispersion ratio does not easily decrease, so that it is easy to achieve both a desired high partial dispersion ratio, a high refractive index, and an Abbe number. On the other hand, devitrification of the glass at the time of producing glass can be reduced by making this mass sum 80.0% or less. Accordingly, the mass sum of the content of the Ln ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably more than 43.0%, more preferably 45.0%, still more preferably 50.0%, Most preferably, the lower limit is 55.0%, preferably 80.0%, more preferably 78.0%, and most preferably 75.0%.

The MgO component, CaO component, SrO component, and BaO component are components that improve the meltability of the glass and increase the devitrification resistance, and are optional components in the optical glass of the present invention. In particular, the content of MgO component is 10.0% or less, the content of CaO component or SrO component is 15.0% or less, or the content of BaO component is 25.0% or less. The rate can be made difficult to decrease. Therefore, the content of the MgO component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. Further, the content of the CaO component and the SrO component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 12.0%, and most preferably 10.0%. Further, the content of the BaO component with respect to the total glass mass of the oxide conversion composition is preferably 25.0%, more preferably 20.0%, and most preferably 15.0%. The MgO component, CaO component, SrO component and BaO component use, for example, MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) _{2 and the} like as raw materials. Can be contained in the glass.

  In the optical glass of the present invention, the mass sum of the content of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 20.0% or less. preferable. Thereby, it is possible to make it difficult to lower the refractive index of the glass. Therefore, the upper limit of the mass sum of the content of the RO component with respect to the total glass mass of the oxide conversion composition is preferably 20.0%, more preferably 15.0%, and most preferably 10.0%.

The SiO ₂ component is a component that promotes stable glass formation and suppresses devitrification (generation of crystalline substances) when producing an unfavorable glass as an optical glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the SiO ₂ component to 25.0% or less, the SiO ₂ component can be easily dissolved in the molten glass, and dissolution at a high temperature can be avoided. The content of the SiO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 25.0%, more preferably 20.0%, and most preferably 15.0%. Note that even without containing a SiO ₂ component, it is possible to obtain a glass having a desired high partial dispersion ratio, by setting the content of SiO ₂ component to 0.1% or more, the glass denitrification Permeability can be increased. Therefore, the content of the SiO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 0.1%, more preferably 0.5%, and most preferably 1.0%. SiO ₂ component may be contained in the glass by using as a raw material such as _{SiO 2, K 2 SiF 6,} Na 2 SiF 6 or the like.

The ZnO component is a component that improves the meltability of the glass, lowers the glass transition point, and easily forms a stable glass, and is an optional component in the optical glass of the present invention. In particular, when the content of the ZnO component is 15.0% or less, the photoelastic constant of the optical glass can be kept low. Therefore, the polarization characteristics of the transmitted light of the optical glass can be improved, and as a result, the color rendering properties of the projector and camera can be improved. Therefore, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, still more preferably 8.7%, and even more preferably 7.7%, Most preferably, the upper limit is 5.0%. The ZnO component can be contained in the glass using, for example, ZnO, ZnF ₂ or the like as a raw material.

The GeO ₂ component is a component having an effect of increasing the refractive index of the glass and improving the devitrification resistance, and is an optional component in the optical glass of the present invention. However, since GeO ₂ has a high raw material price, if the amount thereof is large, the material cost becomes high, and the resulting glass becomes impractical. Therefore, the content of the GeO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The GeO ₂ component can be contained in the glass using, for example, GeO ₂ as a raw material.

P ₂ O ₅ component is a component having an effect of improving resistance to devitrification and lower the liquidus temperature of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress a decrease in chemical durability, particularly water resistance, of the glass. Therefore, the content of the P ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The P ₂ O ₅ component can be contained in the glass using, for example, Al (PO ₃ ) ₃ , Ca (PO ₃ ) ₂ , Ba (PO ₃ ) ₂ , BPO ₄ , H ₃ PO ₄ or the like as a raw material. .

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are components that facilitate the formation of stable glass, and are optional components in the optical glass of the present invention. In particular, when the contents of the Al ₂ O ₃ component and the Ga ₂ O ₃ component are each 10.0% or less, a decrease in the Abbe number of the glass can be suppressed. Therefore, the content of the Al ₂ O ₃ component and the Ga ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%, respectively. Is the upper limit. The Al ₂ O ₃ component and the Ga ₂ O ₃ component should be contained in the glass using, for example, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga (OH) _3, etc. as raw materials. Can do.

Na 2 _O component is a component for improving the meltability of the glass, an optional component of the optical glass of the present invention. In particular, by making the content of the Na ₂ O component 10.0% or less, the refractive index of the glass is hardly lowered, the stability of the glass is increased, and devitrification and the like are hardly caused. Accordingly, the content of the Na ₂ O component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The Na ₂ O component can be contained in the glass using, for example, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ or the like as a raw material.

The SnO ₂ component is a component that reduces the oxidation of the molten glass to clarify the molten glass and makes it difficult to deteriorate the transmittance of the glass against light irradiation, and is an optional component in the optical glass of the present invention. In particular, when the content of the SnO ₂ component is 1.0% or less, it is possible to make it difficult to cause coloration of the glass due to the reduction of the molten glass and devitrification of the glass. Further, since the alloying of the SnO ₂ component and the melting equipment (especially a noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the content of the SnO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 0.7%, and most preferably 0.5%. The SnO ₂ component can be contained in the glass using, for example, SnO, SnO ₂ , SnF ₂ , SnF ₄ or the like as a raw material.

The Sb ₂ O ₃ component is a component that defoams the molten glass and is an optional component in the optical glass of the present invention. In particular, by setting the content of _Sb 2 _{O 3} ingredient 1.0% or less, can be hardly caused excessive foaming during glass melting, _Sb 2 _{O 3} ingredient is dissolved facilities (especially noble metal such as Pt ) And alloying can be made difficult. Therefore, the upper limit of the content of the Sb ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 0.8%, and most preferably 0.5%. The Sb ₂ O ₃ component can be contained in the glass using, for example, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ · 5H ₂ O, or the like as a raw material.

Incidentally, components defoamed fining glass is not limited to the above Sb ₂ O ₃ component, a known refining agents in the field of glass production, it is possible to use a defoamer or a combination thereof.

<About ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferably contained will be described.

If necessary, other components can be added to the optical glass of the present invention as long as the properties of the glass of the present invention are not impaired. However, it is preferable that the GeO ₂ component is not substantially contained since it increases the dispersibility of the glass.

  In addition, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, except Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, is independent of each other. Or, even when it is contained in a small amount in combination, the glass is colored and has the property of causing absorption at a specific wavelength in the visible range. .

Furthermore, lead compounds such as PbO, arsenic compounds such as As ₂ O ₃ , and components of Th, Cd, Tl, Os, Be, and Se have been refraining from being used as harmful chemical substances in recent years. Environmental measures are required not only in the manufacturing process but also in the processing process and disposal after commercialization. Therefore, when importance is placed on the environmental impact, it is preferable not to substantially contain them except for inevitable mixing. As a result, the optical glass is substantially free of substances that pollute the environment. Therefore, the optical glass can be manufactured, processed, and discarded without taking any special environmental measures.

The glass composition of the present invention cannot be expressed directly in the description of mol% because the composition is expressed by mass% with respect to the total mass of the glass of oxide conversion composition, but various properties required in the present invention. The composition expressed by mol% of each component present in the glass composition satisfying the above conditions generally takes the following values in terms of oxide conversion.
B ₂ O ₃ component 10.0～75.0Mol% and _La 2 _{O 3} component 5.0～25.0Mol%
And _Bi 2 _{O 3} component 0～4.0Mol% and / or TiO ₂ component 0～30.0Mol% and / or WO ₃ components 0～10.0Mol% and / or _Nb 2 _{O 5} component 0～10.0Mol% and / or _{K 2} O ingredient 0～15.0Mol% and / or _Ta 2 _{O 5} component 0～5.0Mol% and / or ZrO ₂ component 0～25.0Mol% and / or Li ₂ O component 0-25. 0 mol% and / or _Gd 2 _{O 3} component 0～20.0Mol% and / or _Y 2 _{O 3} component 0～15.0Mol% and / or _Yb 2 _{O 3} component 0～10.0Mol% and / or _Lu 2 O ₃ components 0 to 10.0 mol% and / or MgO components 0 to 35.0 mol% and / or CaO components 0 to 35.0 mol% and / or SrO components 0 to 25.0 mol% and / or Ba O component 0～25.0Mol% and / or SiO ₂ component 0～60.0Mol% and / or ZnO component 0～30.0Mol% and / or GeO ₂ component 0～20.0Mol% and / or _P 2 _{O 5} component 0～10.0Mol% and / or _Al 2 _{O 3} component 0～20.0Mol% and / or _Ga 2 _{O 3} component 0～8.0Mol% and / or Na ₂ O component 0～25.0Mol% and / or SnO ₂ component 0～1.0Mol% and / or _Sb 2 _{O 3} component 0～0.5Mol%
In addition, the total amount of fluoride as F substituted with part or all of one or more oxides of each of the above metal elements as 0 to 75.0 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible, a quartz crucible or an alumina crucible and roughly melted, then a gold crucible, a platinum crucible In a platinum alloy crucible or iridium crucible, melt in a temperature range of 1300 to 1350 ° C. for 3 to 4 hours, stir and homogenize, blow out bubbles, etc., then lower the temperature to 1200 ° C. or lower and perform final stirring It is manufactured by removing the striae, casting into a mold and slow cooling.

[Physical properties]
The optical glass of the present invention preferably has a predetermined refractive index and dispersion (Abbe number). More specifically, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.73, more preferably 1.75, and most preferably 1.77. On the other hand, the upper limit of the refractive index (n _d ) of the optical glass of the present invention is not particularly limited, but is generally 2.20 or less, more specifically 2.10 or less, and more specifically 2.00 or less. There are many. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 45, more preferably 47, and most preferably 49. On the other hand, the upper limit of the Abbe number (ν _d ) of the optical glass of the present invention is not particularly limited, but is generally 60 or less, more specifically 58 or less, and more specifically 57 or less. As a result, the degree of freedom in optical design is increased, and a large amount of light refraction can be obtained even if the device is made thinner.

Moreover, the optical glass of the present invention has a high partial dispersion ratio (θg, F). More specifically, the partial dispersion ratio (θg, F) of the optical glass of the present invention is (θg, F) ≧ −0.00170 × ν _d +0.63750) with the Abbe number (ν _d ). Satisfy the relationship. With the optical glass of the present invention, an optical glass having a higher partial dispersion ratio (θg, F) than a conventionally known glass containing a large amount of rare earth element components can be obtained. Therefore, chromatic aberration of an optical element formed from the optical glass can be reduced while achieving high refractive index and low dispersion of the glass. Here, the lower limit of the partial dispersion ratio (θg, F) of the optical glass is preferably (−0.00170 × ν _d +0.63750), more preferably (−0.00170 × ν _d +0.63950), Preferably, it is (−0.00170 × ν _d +0.64150). On the other hand, the upper limit of the partial dispersion ratio (θg, F) of the optical glass of the present invention is not particularly limited, but for example (−0.00170 × ν _d +0.65750), more preferably (−0.00170 × ν). _d +0.65550), and most preferably (−0.00170 × ν _d +0.653750).

  The partial dispersion ratio (θg, F) of the optical glass of the present invention is measured based on Japanese Optical Glass Industry Association Standard JOGIS01-2003. In addition, the glass used for this measurement uses what was processed in the slow cooling furnace by making slow cooling temperature-fall rate into -25 degrees C / hr.

  The optical glass of the present invention preferably has a glass transition point (Tg) of 650 ° C. or lower. As a result, press molding at a lower temperature is possible, so that the oxidation of the mold used for mold press molding can be reduced to extend the life of the mold. Therefore, the upper limit of the glass transition point (Tg) of the optical glass of the present invention is preferably 650 ° C., more preferably 620 ° C., and most preferably 600 ° C. The lower limit of the glass transition point (Tg) of the optical glass of the present invention is not particularly limited, but the glass transition point (Tg) of the glass obtained by the present invention is generally 100 ° C. or higher, specifically 150 ° C. or higher. More specifically, it is often 200 ° C. or higher.

  The glass transition point (Tg) of the optical glass of the present invention is determined by performing measurement using a differential heat measuring device (STA 409 CD manufactured by Netchgeretebau). Here, the sample particle size at the time of measurement is set to 425 to 600 μm, and the heating rate is set to 10 ° C./min.

Moreover, it is preferable that the optical glass of this invention has little coloring. In particular, when the optical glass of the present invention is represented by the transmittance of the glass, the wavelength (λ ₇₀ ) showing a spectral transmittance of 70% in a sample having a thickness of 10 mm is 500 nm or less, more preferably 480 nm or less, and most preferably. Is 450 nm or less. In the optical glass of the present invention, a wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 450 nm or less, more preferably 430 nm or less, and most preferably 410 nm or less. Thereby, the absorption edge of the glass is positioned in the vicinity of the ultraviolet region, and the transparency of the glass in the visible region is enhanced. Therefore, this optical glass can be used as a material for an optical element such as a lens.

The transmittance of the optical glass of the present invention is measured according to Japan Optical Glass Industry Association Standard JOGIS02. Specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm in accordance with JISZ8722, and λ ₇₀ (wavelength at 70% transmittance) and λ ₅ (transmittance). (Wavelength at 5%).

The optical glass of the present invention preferably has a small photoelastic constant. In particular, the optical glass of the present invention has a photoelastic constant (β) of 2.0 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less at a wavelength of 546.1 nm, more preferably 1.5 × 10 ^{−. 5} nm · cm ⁻¹ · Pa ⁻¹ or less, more preferably 1.0 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less, and most preferably 0.7 × 10 ⁻⁵ nm · cm. ⁻¹ · Pa ⁻¹ or less. As a result, while the partial dispersion ratio of the optical glass is increased, the polarization characteristics of the transmitted light are enhanced. Therefore, when the optical glass is used in an optical system of a projector or a camera (particularly equipped with a polarizing filter), chromatic aberration is obtained. While suppressing this, irregular reflection of light inside the optical element can be suppressed. That is, the color rendering properties in these projectors and cameras can be further enhanced.

The photoelastic constant (β) of the optical glass of the present invention is obtained by using a disk-shaped sample having a diameter of 25 mm and a thickness of 8 mm subjected to facing polishing, and applying a compressive load of F [Pa] in a predetermined direction. An optical path difference δ [nm] of light having a wavelength of 546.1 nm generated at the center is measured. Then, using the obtained values of F and δ and the value of the glass thickness d [cm], the photoelastic constant β [10 ⁻⁵ nm · cm ⁻¹ · Pa- ¹ ] is obtained. Note that an ultra-high pressure mercury lamp is used as a measurement light source having a wavelength of 546.1 nm.

[Preforms and optical elements]
A glass molded body can be produced from the produced optical glass by means of mold press molding such as reheat press molding or precision press molding. That is, a preform for mold press molding is prepared from optical glass, and after performing reheat press molding on the preform, polishing is performed to prepare a glass molded body, or for example, polishing is performed. The preform can be precision press-molded to produce a glass molded body. In addition, the means for producing the glass molded body is not limited to these means.

  The glass molded body thus produced is useful for various optical elements, and among them, it is particularly preferable to use it for applications of optical elements such as lenses and prisms. As a result, color bleeding due to chromatic aberration in the transmitted light of the optical system provided with the optical element is reduced. Therefore, when this optical element is used in a camera, a photographing object can be expressed more accurately, and when this optical element is used in a projector, a desired image can be projected with higher definition.

The compositions of Examples (No. 1 to No. 13) and Comparative Examples (No. 1) of the present invention, and the values of the refractive index (n _d ) and Abbe number (ν _d ) of these glasses are shown in Tables 1 to 1. It shows in Table 2. The following examples are merely for illustrative purposes, and are not limited to these examples.

  The optical glass of Examples (No. 1 to No. 13) of the present invention and the glass of Comparative Example (No. 1) are all oxides, hydroxides, carbonates and nitrates corresponding to the raw materials of the respective components. Select high-purity raw materials used for ordinary optical glass such as fluoride, hydroxide, and metaphosphoric acid compounds, and make the composition ratios of the examples and comparative examples shown in Tables 1 and 2 After weighing and mixing uniformly, it is put in a platinum crucible and melted in a temperature range of 1300 to 1350 ° C. for 3 to 4 hours in accordance with the melting difficulty of the glass composition, and homogenized by stirring to remove bubbles. Then, the temperature was lowered to 1150 ° C. or lower, and the mixture was homogenized with stirring, cast into a mold, and slowly cooled to produce glass.

Here, the refractive index (n _d ) and Abbe number (ν _d ) of the glass of Examples (No. 1 to No. 13) and Comparative Example (No. 1) are in accordance with the Japan Optical Glass Industry Association Standard JOGIS01-2003. Measured based on. In addition, the glass used for this measurement used what was processed in the slow cooling furnace by making slow cooling temperature-fall rate into -25 degrees C / hr.

The optical glass of the example of the present invention has a partial dispersion ratio (θg, F) of (−0.00170 × ν _d +0.63750) or more, and is presumed to have a desired high partial dispersion ratio. Therefore, it is considered that the optical glass of the example of the present invention has a large partial dispersion ratio (θg, F) in the relational expression with the Abbe number (ν _d ) and a small chromatic aberration when the optical element is formed.

The optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.73 or more, and this refractive index (n _d ) is 2.20 or less, more specifically 1.78 or less. And within the desired range.

The optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 45 or more, more specifically 49 or more, and this Abbe number (ν _d ) of 60 or less, more specifically 54. And within the desired range.

The optical glass of the example of the present invention has a glass transition point (Tg) of 650 ° C. or less, λ ₇₀ (wavelength at 70% transmittance) is 500 nm or less, and λ ₅ (at 5% transmittance). It is presumed that the photoelastic constant (β) at a wavelength of 546.1 nm is 2.0 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less.

Therefore, the optical glass of the embodiment of the present invention has a small refractive index (n _d ) and Abbe number (ν _d ) within a desired range, and has small chromatic aberration, is easy to perform mold press molding, and has a wavelength in the visible region. It is considered that the transparency to light is high and the irregular reflection inside the optical glass is small.

  Furthermore, using the optical glass obtained in the example of the present invention, after performing reheat press molding, grinding and polishing were performed to process into the shape of a lens and a prism. Further, a precision press-molding preform was formed using the optical glass of the example of the present invention, and the precision press-molding preform was precision press-molded. In either case, the glass after heat softening did not cause problems such as opacification and devitrification, and could be stably processed into various lens and prism shapes.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (13)

Excluding the entire mass of the glass in terms of oxide composition, _B 2 _{O 3} ingredient 5.0% or more 35.0% or less by mass% _(however, those containing B 2 _{O 3} component or 25.0% ),
La ₂ O ₃ component 20.0-55.0%
Contains,
The content of SiO ₂ component is 15.0% or less,
The content of the ZnO component is 5.0% or less, and the content of the F component is 1.0% or more and 30.0% or less by the outer mass% with respect to the total glass mass of the oxide conversion composition,
The mass sum (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) with respect to the total glass mass of the oxide conversion composition is 10.00% or more,
Mass sum of Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) with respect to the total glass mass of the oxide equivalent composition is more than 43.0% 80.0% or less,
It has a refractive index (n _d ) of 1.73 or more and an Abbe number (ν _d ) of 45 or more, and the partial dispersion ratio (θg, F) is (θg, F) between the Abbe number (ν _d ). ) ≧ (−0.00170 × ν _d +0.63750). Bi ₂ O ₃ component 0 to 10.0% and / or TiO ₂ component 0 to 15.0% and / or WO ₃ component 0 to 15.0% by mass% with respect to the total glass mass of the oxide conversion composition And / or Nb ₂ O ₅ component 0 to 20.0% and / or K ₂ O component 0 to 10.0%
The optical glass according to claim 1, further comprising: Ta ₂ O ₅ component 0 to 15.0% and / or ZrO ₂ component 0 to 15.0% and / or Li ₂ O component 0 to 5.0 by mass% with respect to the total glass mass of oxide conversion composition %
The optical glass according to claim 1 or 2. 4. The optical glass according to claim 3, wherein a mass ratio (F + Bi ₂ O ₃ + TiO ₂ + WO ₃ + Nb ₂ O ₅ + K ₂ O) / (Ta ₂ O ₅ + ZrO ₂ + Li ₂ O) of the oxide equivalent composition is 1.3 or more. . The entire mass of the glass in terms of oxide composition, 0~40.0% _Gd 2 _{O 3} component in% by weight and / or _Y 2 _{O 3} component from 0 to 20.0% and / or _Yb 2 _{O 3} component 0 20.0% and / or Lu ₂ O ₃ component 0-20.0%
The optical glass according to claim 1, further comprising: The optical glass according to any one of claims 1 to 5, wherein the content of Gd ₂ O ₃ is 29.5% or less by mass based on the total mass of the oxide-converted composition. MgO component 0 to 10.0% and / or CaO component 0 to 15.0% and / or SrO component 0 to 15.0% and / or BaO component in mass% with respect to the total glass mass of the oxide conversion composition 0-25.0%
The optical glass according to claim 1, further comprising:   The mass sum of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) with respect to the total glass mass of the oxide equivalent composition is 20.0% or less. Optical glass. GeO ₂ component 0 to 10.0% and / or P ₂ O ₅ component 0 to 10.0% and / or Al ₂ O ₃ component 0 to 10% by mass with respect to the total glass mass of the oxide equivalent composition. 0% and / or Ga ₂ O ₃ component 0 to 10.0% and / or Na ₂ O component 0 to 10.0% and / or SnO ₂ component 0 to 1.0% and / or Sb ₂ O ₃ component 0 to 1.0%
The optical glass according to claim 1, further comprising:   A preform material comprising the optical glass according to claim 1.   An optical element produced by press-molding the preform material according to claim 10.   An optical element using the optical glass according to claim 1 as a base material.   An optical apparatus comprising the optical element according to claim 11.

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