JP2010006692A - Optical glass, optical element and preform for precision press molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass which has high thermal stability and has a reduced chromatic aberration while its refractive index (n<SB>d</SB>) and Abbe number lies within desired ranges, and to provide an optical element and a preform for precision press molding using the optical glass. <P>SOLUTION: The optical glass comprises, to the whole mass of the glass in a composition expressed in terms of oxide, by mol%, a TeO<SB>2</SB>component of 10.0 to 95.0% and a GeO<SB>2</SB>component of 1.0 to 55.0%. The optical glass comprises, to the whole mass of the glass in a composition expressed in terms of oxide, by mol, a TeO<SB>2</SB>component of 10.0 to 95.0% and a GeO<SB>2</SB>component of 1.0 to 55.0%. The optical element and preform for precision press forming are composed of the optical glass. By jointly using the TeO<SB>2</SB>component and the GeO<SB>2</SB>component, and suppressing the contents of the TeO<SB>2</SB>component and the GeO<SB>2</SB>component to the above ranges, the refractive index (n<SB>d</SB>) of the glass is increased, its Abbe number (ν<SB>d</SB>) reaches a desired range, the difference ΔT between the glass transition point (Tg) and the crystallization starting temperature (Tx) is made wide, a desired relationship is brought about between the partial dispersion ratio (θg, F) of the glass and the Abbe number (ν<SB>d</SB>), and abnormal partial dispersion is made small. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical glass, an optical element, and a precision press-molding preform.

  In recent years, the digitization and high definition of devices that use optical systems have been rapidly progressing, and the precision of optical elements such as lenses used in various optical devices, including photography devices such as digital cameras and video cameras, The demand for light weight and downsizing is increasing.

Among optical glasses for producing optical elements, in particular, it has a high refractive index (n _d ) of 1.85 or more and 2.20 or less, which can reduce the weight and size of the optical element, and is 10 or more and 40 or less. There is a great demand for high refractive index glass having an Abbe number (ν _d ) of. As such a high refractive index glass, glass compositions represented by Patent Documents 1 to 4 are known. For example, the glass composition of Patent Document 1 is known as an optical glass having a refractive index (n _d ) of 1.80 to 2.20 and an Abbe number (ν _d ) of 18 to 42, and the refractive index (n The glass composition of Patent Document 2 is known as an optical glass having _d ) of 1.80 or more, and the glass composition of Patent Document 3 is known as an optical glass having a refractive index (n _d ) of 1.85 or more. Yes. Further, as an optical glass having a refractive index (n _d ) of 1.8 or more and an Abbe number of around 20, a glass composition of Patent Document 4 is known.

JP-A 61-197443 JP 2002-241144 A JP 2004-43294 A JP 2001-180971 A

  As a method for manufacturing such an optical element, a preform material obtained by cutting and polishing a gob or a glass block, or a preform material formed by a known floating molding or the like is heated and softened to have a highly accurate molding surface. The pressure molding method (precision press molding) is used.

  However, in the glasses disclosed in Patent Documents 1, 2, and 3, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) was small, and the thermal stability of these glasses was low. Therefore, when a preform material is produced from this glass and an optical element is produced by heat-softening and molding the preform material, the produced optical element is devitrified due to crystallization of the heat-softened glass. The optical characteristics of the element were affected.

  The glass disclosed in Patent Document 4 has a large refractive index, but has a large difference in refractive index with respect to the wavelength of light to be transmitted, and an optical element formed from the glass has large chromatic aberration. .

Here, it is known that the chromatic aberration of the optical element is closely related to the partial dispersion ratio (θg, F). Here, the partial dispersion ratio (θg, F) representing the partial dispersion in the short wavelength region is shown in 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, particularly high-dispersion glass (low Abbe number (ν _d )) has a value in which the partial dispersion ratio (θg, F) of the glass is away from the normal line. Therefore, when an optical element is manufactured using these highly dispersed glasses, chromatic aberration is generated in the optical element, so that it is necessary to correct the chromatic aberration.

The present invention has been made in view of the above problems, and its object is to achieve high thermal stability while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. It is an object to obtain an optical glass having good properties and reduced chromatic aberration, an optical element using the optical glass, and a preform for precision press molding.

In order to solve the above-mentioned problems, the present inventors have conducted earnest test research. As a result, by using a TeO ₂ component and a GeO ₂ component in combination, the refractive index (n _d ) of the glass is increased and the Abbe number ( [nu _d) it is in a desired range, as well as a combination of TeO ₂ component and GeO ₂ component, by suppressing the content of TeO ₂ component and GeO ₂ component in the above range, the glass transition point and (Tg) The difference ΔT from the crystallization start temperature (Tx) is increased, and a desired relationship is brought about between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) of the glass. It came to be completed. Specifically, the present invention provides the following.

(1) An optical glass containing 10.0 to 95.0% of a TeO ₂ component and 1.0 to 55.0% of a GeO ₂ component in mol% with respect to the total amount of the glass having an oxide conversion composition.

(2) The optical glass according to (1), wherein a substance amount ratio TeO ₂ / GeO ₂ having an oxide equivalent composition is less than 13.0.

(3) the glass the total amount of substance of the oxide composition in terms of, from 0 to 20.0% Li ₂ O component in mol% and / or Na ₂ O component from 0 to 20.0% and / or _{K 2} O ingredient 0 20.0% and / or Cs ₂ O component from 0 to 20.0%
The optical glass according to (1) or (2), further containing each component of

(4) 0 to 15.0% of MgO component and / or 0 to 20.0% of CaO component and / or 0 to 20.0% of SrO component in mol% with respect to the total amount of glass in the oxide conversion composition / Or BaO component 0 to 20.0%
The optical glass according to any one of (1) to (3), further comprising:

(5) The optical glass according to (4), wherein a substance amount sum (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) with respect to the total glass substance amount of an oxide conversion composition is 5.0% or more and 30.0% or less.

(6) ZrO ₂ component 0 to 20.0% and / or Ta ₂ O ₅ component 0 to 20.0% and / or Nb ₂ O ₅ component in mol% with respect to the total amount of glass in the oxide conversion composition 0 to 30.0% and / or La ₂ O ₃ component 0 to 30.0% and / or Gd ₂ O ₃ component 0 to 30.0% and / or Y ₂ O ₃ component 0 to 20.0% and / or or _Yb 2 _{O 3} component from 0 to 20.0% and / or _Ga 2 _{O 3} component from 0 to 25.0% and / or _In 2 _{O 3} component from 0 to 25.0% and / or _Bi 2 _{O 3} component 0 50.0%
The optical glass according to any one of (1) to (5), further comprising:

(7) Material quantity ratio of oxide conversion composition (TeO ₂ ) / (100-TeO ₂ — (ZrO ₂ + Ta ₂ O ₅ + Nb ₂ O ₅ + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Ga) ₂ O ₃ + In ₂ O ₃ + Bi ₂ O ₃ )) is 2.00 or more, the optical glass according to (6).

(8) the glass the total amount of substance of the oxide composition in terms of, 0-30.0% ZnO component in mol% and / or _Al 2 _{O 3} component from 0 to 20.0% and / or _B 2 _{O 3} component 0 -50.0% and / or SiO ₂ component 0-30.0% and / or P ₂ O ₅ component 0-50.0% and / or WO ₃ component 0-25.0% and / or TiO ₂ component 0 30.0% and / or _Sb 2 _{O 3} component from 0 to 1.0% and / or CeO ₂ component from 0 to 1.0%
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), which has a refractive index (n _d ) of 1.85 or more and 2.20 or less and an Abbe number (ν _d ) of 10 or more and 40 or less.

  (10) The optical glass according to any one of (1) to (9), wherein a difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is 95 ° C. or more.

  (11) The optical glass according to any one of (1) to (10), wherein a difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is 105 ° C. or higher.

(12) (−0.0016 × ν _d +0.6346) ≦ (θg, F) ≦ () in the range where the partial dispersion ratio (θg, F) is Abbe number (ν _d ) and ν _d ≦ 25. −0.0058 × ν _d +0.7539), and (−0.0025 × ν _d +0.6571) ≦ (θg, F) ≦ −0.0020 × ν _d +0 in the range of ν _d > 25. . The optical glass according to any one of (1) to (11), which satisfies the relationship of 6589.

  (13) An optical element formed by precision press molding the optical glass according to any one of (1) to (12).

  (14) A precision press-molding preform comprising the optical glass according to any one of (1) to (12).

  (15) An optical element obtained by precision press molding the preform for precision press molding according to (14).

According to the present invention, by using a TeO ₂ component and a GeO ₂ component in combination, the refractive index (n _d ) of the glass is increased, and the Abbe number (ν _d ) falls within a desired range. Moreover, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is obtained by using the TeO ₂ component and the GeO ₂ component together and suppressing the content of the TeO ₂ component and the GeO ₂ component within the above range. Increases, transparency of the glass in the visible region is enhanced, and a desired relationship is brought about between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) of the glass, thereby reducing the abnormal partial dispersion. . Therefore, an optical glass having high thermal stability, little coloring, and reduced chromatic aberration while having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges, and The used optical element and optical apparatus 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. It is a figure which shows the relationship between the partial dispersion ratio ((theta) g, F) and the Abbe number ((nu) _d ) about the glass of the Example of this application.

The optical glass of the present invention contains 10.0 to 95.0% of the TeO ₂ component and 1.0 to 55.0% of the GeO ₂ component in mol% with respect to the total amount of the glass having the oxide conversion composition. To do. By using the TeO ₂ component and the GeO ₂ component in combination, the refractive index (n _d ) of the glass is increased and the Abbe number (ν _d ) is in a desired range. Moreover, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is obtained by using the TeO ₂ component and the GeO ₂ component together and suppressing the content of the TeO ₂ component and the GeO ₂ component within the above range. Increases the thermal stability of the glass. Moreover, since the transparency of the glass in a visible region is improved by using the TeO ₂ component and the GeO ₂ component together and suppressing the content ratio of the TeO ₂ component and the GeO ₂ component within the above range, the coloring of the glass is reduced. be able to. Further, by using the TeO ₂ component and the GeO ₂ component in combination, the partial dispersion ratio (θg, F) of the glass has a desired relationship with the Abbe number (ν _d ), and the abnormal partial dispersion is reduced. Therefore, it has high thermal stability, little coloring, small chromatic aberration, and a refractive index (n _d ) of 1.85 or more and 2.20 or less and an Abbe number (ν _d ) of 10 or more and 40 or less. Optical glass can be obtained.

  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 the present specification, unless otherwise specified, the content of each component is all expressed in mol% with respect to the total amount of glass having an oxide equivalent 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 substance amount of the said production | generation oxide into 100 mol%.

<About essential and optional components>
The TeO ₂ component is a component that increases the refractive index of the glass. In particular, by making the content of the TeO ₂ component 10.0% or more, a desired high refractive index can be easily obtained. On the other hand, by setting the content of the TeO ₂ component to 95.0% or less, the partial dispersion ratio (θg, F) of the glass can be lowered while reducing the devitrification resistance of the glass. Accordingly, the content of the TeO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 10.0%, more preferably 13.0%, most preferably 15.0%, and preferably 95. The upper limit is 0%, more preferably 92.0%, and most preferably 90.0%. The TeO ₂ component can be contained in the glass using, for example, TeO ₂ as a raw material.

The GeO ₂ component is a component that constitutes a glass network and contributes to an increase in the refractive index of the glass. In particular, the desired high refractive index can be easily obtained by setting the content of the GeO ₂ component to 1.0% or more. On the other hand, by setting the content of the GeO ₂ component below 55.0%, it is possible to reduce the material cost of the glass. Accordingly, the content of the GeO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 1.0%, more preferably 3.0%, and most preferably 5.0%, preferably 55. The upper limit is 0%, more preferably 50.0%, and most preferably 45.0%. The GeO ₂ component can be contained in the glass using, for example, GeO ₂ as a raw material.

In the optical glass of the present invention, the ratio of the amount of TeO ₂ component to the content of GeO ₂ component is preferably less than 13.0. By making this substance amount ratio less than 13.0, the thermal stability of the glass can be further improved, and thus devitrification when the optical glass is softened by heating can be reduced. Accordingly, the ratio of the amount of the TeO ₂ component to the content of the GeO ₂ component is preferably less than 13.0, more preferably 12.9, and most preferably 12.8. In addition, if the value of this substance amount ratio is within this range, there is no technical disadvantage, but TeO _{2 having} a large effect of increasing the refractive index can be obtained by setting this substance amount ratio to 2.0 or more. Since the substance amount of the component becomes relatively large, the refractive index of the glass can be further increased. The value of the substance amount ratio at this time is preferably 2.0, more preferably 3.0, and most preferably 4.0.

The Li ₂ O component is a component that adjusts the partial dispersion ratio (θg, F) of the glass and lowers the melting point of the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of the Li ₂ O component 20.0% or less, the glass expansion coefficient is reduced, the lens surface is accurately transferred during precision press molding, and the water resistance of the glass is increased. be able to. Therefore, the upper limit of the content ratio of the Li ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 18.0%, and most preferably 15.0%. 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.

The Na ₂ O component is a component that adjusts the partial dispersion ratio (θg, F) of the glass, lowers the melting point of the glass, and stabilizes the glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of Na 2 _O component below 20.0%, it is possible to increase the water resistance of the glass. Therefore, the content of the Na ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 18.0%, and most preferably 15.0%. 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 K ₂ O component is a component that adjusts the partial dispersion ratio (θg, F) of the glass and lowers the melting point of the glass, and is an optional component in the optical glass of the present invention. In particular, the water resistance of the glass can be increased by setting the content of the K ₂ O component to 20.0% or less. Therefore, the upper limit of the content of the K ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 18.0%, and most preferably 15.0%. 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.

The Cs ₂ O component is a component that adjusts the partial dispersion ratio (θg, F) of the glass and lowers the melting point of the glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of Cs 2 _O component below 20.0%, it is possible to increase the water resistance of the glass. Therefore, the upper limit of the content of the Cs ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 18.0%, and most preferably 15.0%. Cs ₂ O component may be contained in the glass by using as the starting material for example _Cs 2 _{CO 3,} CsNO 3, and the like.

The MgO component is a component that increases the transmittance in the visible region of the glass and improves the solubility and stability of the glass, and is an optional component in the optical glass of the present invention. In particular, the stability of the glass can be easily maintained by setting the content of the MgO component to 15.0% or less. Therefore, the content of the MgO component with respect to the total amount of glass in the oxide conversion composition is preferably 15.0%, more preferably 12.0%, and most preferably 10.0%. The MgO component can be contained in the glass using, for example, MgCO ₃ or MgF ₂ as a raw material.

A CaO component is a component which improves the transmittance | permeability in the visible region of glass, improves the solubility and stability of glass, and is an arbitrary component in the optical glass of this invention. In particular, the stability of the glass can be easily maintained by setting the content of the CaO component to 20.0% or less. Therefore, the upper limit of the CaO component content with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The CaO component can be contained in the glass using, for example, CaCO ₃ , CaF ₂ or the like as a raw material.

The SrO component is a component that increases the transmittance in the visible region of the glass and improves the solubility and stability of the glass, and is an optional component in the optical glass of the present invention. In particular, the stability of the glass can be easily maintained by setting the content of the SrO component to 20.0% or less. Therefore, the upper limit of the content of the SrO component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The SrO component can be contained in the glass using, for example, Sr (NO ₃ ) ₂ , SrF ₂ or the like as a raw material.

The BaO component is a component that improves the solubility and stability of the glass, and is an optional component in the optical glass of the present invention. In particular, the stability of the glass can be easily maintained by setting the content of the BaO component to 20.0% or less. Therefore, the upper limit of the content of the BaO component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 19.0%, and most preferably 18.0%. The BaO component can be contained in the glass using, for example, BaCO ₃ , Ba (NO ₃ ) ₂ or the like as a raw material.

In the optical glass of the present invention, the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, K, and Cs) and the RO component (wherein R is Mg, Ca, Sr, It is preferable that the substance amount sum of the content ratio of one or more selected from the group consisting of Ba is 5.0% or more and 30.0% or less. By setting the amount of this substance to 5.0% or more, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is increased, so that the thermal stability of the glass can be increased. Moreover, it can be made easy to form a stable glass by making this amount of substance sum into 30.0% or less. Therefore, the total amount of RO component content relative to the total amount of glass in oxide equivalent composition is preferably 5.0%, more preferably 6.0%, and most preferably 7.0%, preferably Is 30.0%, more preferably 27.0%, and most preferably 25.0%.

The ZrO ₂ component is a component that increases the refractive index of the glass and suppresses devitrification in the process of cooling the glass from the molten state, and is an optional component in the optical glass of the present invention. In particular, when the content of the ZrO ₂ component is 20.0% or less, the glass is easily melted at a lower temperature, so that energy loss during glass production can be reduced. Therefore, the upper limit of the content of the ZrO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The ZrO ₂ component can be contained in the glass using, for example, ZrO ₂ , ZrF ₄ or the like as a raw material.

The Ta ₂ O ₅ component is a component that increases the refractive index of the glass and stabilizes the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of Ta ₂ O ₅ component 20.0% or less, the amount of Ta ₂ O ₅ component, which is a rare mineral resource, is reduced, and the glass is more easily melted at a lower temperature. The production cost can be reduced. Therefore, the content of the Ta ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

The Nb ₂ O ₅ component is a component that increases the partial dispersion ratio (θg, F) of the glass and increases the refractive index and dispersion of the glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the Nb ₂ O ₅ component to 30.0% or less, coloring of the glass when the glass is exposed to ultraviolet light can be reduced. Therefore, the upper limit of the content of the Nb ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 27.0%, and most preferably 25.0%. The Nb ₂ O ₅ component can be contained in the glass using, for example, Nb ₂ O ₅ as a raw material.

The La ₂ O ₃ component is a component that increases the refractive index of the glass and adjusts the dispersion of the glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the La ₂ O ₃ component to 30.0% or less, it is possible to easily maintain good devitrification resistance while maintaining a desired optical constant. Therefore, the content of the La ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 27.0%, and most preferably 25.0%. 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.

Gd ₂ O ₃ component increases the refractive index of the glass is a component that adjusts the dispersion of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the Gd ₂ O ₃ component to 30.0% or less, it is possible to easily maintain good devitrification resistance while maintaining a desired optical constant. Therefore, the content of the Gd ₂ O ₃ component is preferably 30.0%, more preferably 27.0%, and most preferably 25.0% with respect to the total amount of glass in the oxide equivalent composition. 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.

Y ₂ O ₃ component increases the refractive index of the glass is a component that adjusts the dispersion of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the Y ₂ O ₃ component to 20.0% or less, it is possible to easily maintain good devitrification resistance while maintaining a desired optical constant. Therefore, the content of the Y ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The Y ₂ O ₃ component can be contained in the glass using, for example, Y ₂ O ₃ , YF ₃ or the like as a raw material.

Yb ₂ O ₃ component is a component that raises the refractive index of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the Yb ₂ O ₃ component to 20.0% or less, it is possible to easily maintain good devitrification resistance while maintaining a desired optical constant. Therefore, the content of the Yb ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The Yb ₂ O ₃ component can be contained in the glass using, for example, Yb ₂ O ₃ as a raw material.

The Ga ₂ O ₃ component is a component that increases the hardness of the glass and is an optional component in the optical glass of the present invention. In particular, by setting the content of _Ga 2 _{O 3} component below 25.0%, it is possible to increase the stability of the glass. Therefore, the upper limit of the content of the Ga ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 25.0%, more preferably 22.0%, and most preferably 20.0%. The Ga ₂ O ₃ component can be contained in the glass using, for example, Ga ₂ O ₃ as a raw material.

The In ₂ O ₃ component is a component that increases the refractive index of the glass and is an optional component in the optical glass of the present invention. In particular, by setting the content of _In 2 _{O 3} component below 25.0%, it is possible to increase the stability of the glass. Therefore, the content of the In ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 25.0%, more preferably 22.0%, and most preferably 20.0%. The In ₂ O ₃ component can be contained in the glass using, for example, In ₂ O ₃ as a raw material.

The Bi ₂ O ₃ component is a component that increases the partial dispersion ratio (θg, F) of the glass, increases the refractive index of the glass, and decreases the yield temperature (At) of the glass, and is an optional component in the optical glass of the present invention. is there. In particular, by setting the content of _Bi 2 _{O 3} component below 50.0%, it is possible to increase the stability of the glass. Therefore, the content of the Bi ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 50.0%, more preferably 45.0%, and most preferably 40.0%. The Bi ₂ O ₃ component can be contained in the glass using, for example, Bi ₂ O ₃ as a raw material.

In the optical glass of the present invention, (100-TeO ₂ − (ZrO ₂ + Ta ₂ O ₅ + Nb ₂ O ₅ + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Ga ₂ O ₃ + In ₂ O ₃ + Bi ₂ It is preferable that the substance amount ratio of the TeO ₂ component to O ₃ )) is 2.00 or more. The refractive index of glass can be raised more by making this substance amount ratio 2.0 or more. Therefore, the lower limit of the amount ratio of this substance is preferably 2.00, more preferably 2.05, and most preferably 2.10. In addition, if the value of the substance amount ratio is within this range, there is no technical disadvantage, but in order to make it easier to obtain a glass having a high refractive index, preferably 8.00, more preferably Is 7.00, and most preferably 6.00.

A ZnO component is a component which improves the stability of glass, and is an arbitrary component in the optical glass of this invention. In particular, by setting the content of the ZnO component to 30.0% or less, it is possible to make it difficult to raise the melting temperature of the glass. Therefore, the upper limit of the content of the ZnO component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 27.0%, and most preferably 25.0%. The ZnO component can be contained in the glass using, for example, ZnO, ZnF ₂ or the like as a raw material.

The Al ₂ O ₃ component is a component that increases the devitrification resistance of the glass, and is an optional component in the optical glass of the present invention. In particular, the desired refractive index can be easily obtained by setting the content of the Al ₂ O ₃ component to 20.0% or less. Therefore, the upper limit of the content ratio of the Al ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 17.0%, and most preferably 15.0%. The Al ₂ O ₃ component can be contained in the glass using, for example, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ or the like as a raw material.

The B ₂ O ₃ component is a component that constitutes a glass network, increases the devitrification resistance of the glass to homogenize the glass, and increases the partial dispersion ratio (θg, F) of the glass. It is an optional component in the optical glass. In particular, by setting the content of the B ₂ O ₃ component to 50.0% or less, a desired refractive index can be easily obtained, and the stability of the glass can be improved. Therefore, the content of the B ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 50.0%, more preferably 45.0%, and most preferably 40.0%. 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 SiO ₂ component is a component that promotes stable glass formation and reduces devitrification of the glass, and is a component that lowers the partial dispersion ratio (θg, F) of the glass, and is an optional component in the optical glass of the present invention. It is. In particular, when the content of the SiO ₂ component is 30.0% or less, the desired refractive index of the glass can be easily obtained. Therefore, the content of the SiO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 27.0%, and most preferably 25.0%. 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.

P ₂ O ₅ component is a component constituting the network 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 50.0% or less, the devitrification tendency can be reduced and the stability of the glass can be increased. Therefore, the content of the P ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition is preferably 50.0%, more preferably 45.0%, and most preferably 40.0%. 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 WO ₃ component is a component that increases the partial dispersion ratio (θg, F) of the glass and increases the refractive index and dispersibility of the glass, and is an optional component in the optical glass of the present invention. In particular, when the content of the WO ₃ component is 25.0% or less, the coloring of the glass when the glass is exposed to ultraviolet light can be reduced. Accordingly, the content of the WO ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 25.0%, more preferably 22.0%, and most preferably 20.0%. The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

The TiO ₂ component is a component that increases the refractive index of the glass and decreases the liquidus temperature of the glass, and is an optional component in the optical glass of the present invention. In particular, the devitrification property of the glass can be reduced by setting the content of the TiO ₂ component to 30.0% or less. Therefore, the content of the TiO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 27.0%, and most preferably 25.0%. TiO ₂ component may be contained in the glass by using as the starting material for example TiO ₂ or the like.

The Sb ₂ O ₃ component is a component that promotes defoaming of the glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the Sb ₂ O ₃ component to 1.0% or less, excessive foaming at the time of melting the glass can be prevented, and the Sb ₂ O ₃ component can be dissolved in a melting facility (particularly a precious metal such as Pt). ) And alloying can be made difficult. Therefore, the content of the Sb ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably 1.0%, more preferably 0.9%, and most preferably 0.8%. 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.

The CeO ₂ component is a component effective for clarifying the glass, and is an optional component in the optical glass of the present invention. In particular, when the content of the CeO ₂ component is 1.0% or less, an optical glass with good internal quality can be obtained. Accordingly, the CeO ₂ component content relative to the total amount of glass in the oxide equivalent composition is preferably 1.0%, more preferably 0.9%, and most preferably 0.8%. The CeO ₂ component can be contained in the glass using, for example, CeO ₂ as a raw material.

The glass refining agent and defoaming agent are not limited to the above-described Sb ₂ O ₃ component and CeO ₂ component, and well-known refining agents, defoaming agents or combinations thereof in the field of glass production are used. be able to.

<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.

  Other components can be added as necessary within the range not impairing the properties of the glass of the present invention. However, the transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding Ti, are colored in the visible region even when they are contained individually or in combination and in small amounts. In particular, in an optical glass using a wavelength in the visible region, it is preferably substantially not contained.

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 is not expressed directly in terms of mass% because the composition is expressed in terms of mol% with respect to the total amount of glass in the oxide-converted composition, but is required in the present invention. The composition represented by mass% of each component present in the glass composition satisfying the characteristics generally takes the following values in terms of oxide conversion.
TeO ₂ component 10.0-95.0% by mass and GeO ₂ component 0.7-40.0% by mass,
And Li ₂ O component 0 to 5.0 mass% and / or Na ₂ O component 0 to 10.0 mass% and / or K ₂ O component 0 to 15.0 mass% and / or Cs ₂ O component 0 to 35 0.0% by mass and / or MgO component 0-5.0% by mass and / or CaO component 0-10.0% by mass and / or SrO component 0-15.0% by mass and / or BaO component 0-20.0 Mass% and / or ZrO ₂ component 0 to 15.0 mass% and / or Ta ₂ O ₅ component 0 to 45.0 mass% and / or Nb ₂ O ₅ component 0 to 45.0 mass% and / or La ₂ O ₃ component 0 to 55.0 mass% and / or Gd ₂ O ₃ component 0 to 55.0 mass% and / or Y ₂ O ₃ component 0 to 30.0 mass% and / or Yb ₂ O ₃ component 0 30.0% by weight and / or _Ga 2 _{O 3} component from 0 to 25.0 wt%及And / or In ₂ O ₃ component 0 to 35.0 mass% and / or Bi ₂ O ₃ component 0 to 70.0 mass% and / or ZnO component 0 to 15.0 mass% and / or Al ₂ O ₃ component 0 to 15.0% by weight and / or _B 2 _{O 3} component from 0 to 25.0% by weight and / or SiO ₂ component from 0 to 13.0% by weight and / or _P 2 _{O 5} component from 0 to 40.0% by weight And / or WO ₃ component 0 to 35.0 mass% and / or TiO ₂ component 0 to 15.0 mass% and / or Sb ₂ O ₃ component 0 to 2.0 mass% and / or CeO ₂ component 0 to 1 .0 mass%

[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 quartz crucible or an alumina crucible and roughly melted, and then a gold crucible, a platinum crucible, a platinum alloy It is prepared by putting in a crucible or iridium crucible, melting in a temperature range of 700 to 1200 ° C., stirring and homogenizing, blowing out bubbles, etc., then lowering to an appropriate temperature, casting into a mold and slow cooling. .

[Physical properties]
The optical glass of the present invention needs to have a high refractive index and moderate dispersion. In particular, the refractive index of the optical glass of the present invention _{(n d)} is preferably 1.85, more preferably 1.88, and most preferably with a lower limit on 1.90, preferably 2.20, more preferably 2. 15, most preferably 2.10. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 10, more preferably 15, most preferably 18, the lower limit, preferably 40, more preferably 35, and most preferably 30. . 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.

  Further, the optical glass of the present invention needs to have as high a thermal stability as possible. In particular, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is preferably 95 ° C., more preferably 105 ° C., still more preferably 108 ° C., and most preferably 110 ° C. Thereby, a preform material such as a precision press-molding preform was produced from the optical glass of the present invention, and even if an optical element was produced by heating and softening this, including devitrification due to crystallization of the glass, The influence on the optical characteristics of the optical element can be reduced.

Further, the optical glass of the present invention needs to be less colored. 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 460 nm or less. Thereby, since the transparency of the glass in the visible region is enhanced, this optical glass can be used as a material for an optical element such as a lens. For the same reason, the wavelength (λ ₅ ) exhibiting a spectral transmittance of 5% in a sample having a thickness of 10 mm is preferably 410 nm or less, more preferably 400 nm or less, and most preferably 390 nm or less.

Further, the optical glass of the present invention needs to have a partial dispersion ratio (θg, F) close to a normal line. More specifically, the partial dispersion ratio (θg, F) of the optical glass of the present invention is (−0.0016 × ν _d +0...) In the range of ν _d ≦ 25 with respect to the Abbe number (ν _d ). 6346) ≦ (θg, F) ≦ (−0.0058 × ν _d +0.7539), and (−0.0025 × ν _d +0.6571) ≦ (θg) in the range of ν _d > 25. , F) ≦ (−0.0020 × ν _d +0.6589). Accordingly, the position of the plot of the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) is brought close to the normal line (Normal Line) in FIG. 1 while having high dispersion. Therefore, it can be inferred that chromatic aberration due to an optical element using this optical glass is reduced. Here, the partial dispersion ratio (θg, F) of the optical glass at ν _d ≦ 25 is preferably (−0.0016 × ν _d +0.6346), more preferably (−0.0016 × ν _d +0.6366). ), Most preferably (−0.0016 × ν _d +0.6386) as the lower limit, preferably (−0.0058 × ν _d +0.7539), more preferably (−0.0058 × ν _d +0.7519). ), Most preferably (−0.0058 × ν _d +0.7509). The partial dispersion ratio (θg, F) of the optical glass at ν _d > 25 is preferably (−0.0025 × ν _d +0.6571), more preferably (−0.0025 × ν _d +0.6591). Most preferably, (−0.0025 × ν _d +0.6611) is the lower limit, preferably (−0.0020 × ν _d +0.6589), more preferably (−0.0020 × ν _d +0.6569). Most preferably, the upper limit is (−0.0020 × ν _d +0.6559). In particular, in a region where the Abbe number (ν _d ) is small, the partial dispersion ratio (θg, F) of general glass is higher than that of the normal line, and the partial dispersion ratio (θg, F) of general glass is high. And the Abbe number (ν _d ) are represented by a curve (in FIG. 2, a curve rising to the right). However, since it is difficult to approximate this curve, the present invention uses a straight line having a different slope from ν _d = 25 as a partial dispersion ratio (θg, F) lower than that of general glass. Expressed.

[Preforms and optical elements]
The optical glass of the present invention is useful for various optical elements and optical designs. In particular, it is possible to produce an optical element such as a lens from the optical glass of the present invention using means such as precision press molding. preferable. As a result, when used in an optical device such as a camera, it is possible to reduce the size of the optical system in these optical devices while realizing high-definition and high-precision imaging characteristics. In addition, since the chromatic aberration is reduced by the optical element using the optical glass, correction with an optical element having a different partial dispersion ratio (θg, F) is not required when used in an optical device such as a camera or a projector. High-definition and high-precision imaging characteristics can be realized. Here, in order to produce an optical element made of the optical glass of the present invention, it is possible to omit cutting and polishing, so that glass in a molten state is dropped from an outlet of an outflow pipe of platinum or the like to form a spherical shape. It is preferable to prepare a precision press-molding preform such as, and perform precision press-molding on the precision press-molding preform.

Composition of glass of Examples (No. 1 to No. 8) of the present invention, refractive index (n _d ), Abbe number (ν _d ), partial dispersion ratio (θg, F), glass transition of these glasses The point (Tg), the crystallization start temperature (Tx), the difference between the glass transition point and the crystallization start temperature (ΔT), and the wavelength (λ ₇₀ , λ ₅ ) at which the spectral transmittance is 70% and 5%. Table 1 shows. FIG. 2 shows the relationship between the Abbe number (ν _d ) and the partial dispersion ratio (θg, F) in the glass of Examples (No. 1 to No. 8). The following examples are merely for illustrative purposes, and are not limited to these examples.

  The optical glasses of Examples (No. 1 to No. 8) of the present invention are all oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, metaphosphoric acids corresponding to the raw materials of the respective components. Select high-purity raw materials used for ordinary optical glass such as compounds, weigh and mix uniformly to the composition ratio of each example shown in Table 1, then put into quartz crucible or platinum crucible Then, it was melted in a temperature range of 700 to 1200 ° C. in an electric furnace according to the melting difficulty of the glass composition, stirred and homogenized, cast into a mold, and slowly cooled to produce a glass.

Here, the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio (θg, F) of the optical glass of Examples (No. 1 to No. 8) are set to −25. It calculated | required by measuring based on Japan Optical Glass Industry Association Standard JOGIS01-2003 about the glass obtained by making into degrees C / h. Then, with respect to the obtained Abbe number (ν _d ) and partial dispersion ratio (θg, F), the slope a in the relational expression (θg, F) = − a × ν _d + b is 0.0016, 0.0020. , 0.0025 and 0.0058 were obtained.

  Moreover, (DELTA) T of the optical glass of an Example (No.1-No.8) is the glass transition point (Tg) measured using the differential-thermal-measurement apparatus (STAC409CD by a Netchgeretebau company), and crystallization start temperature ( It was determined from the difference of Tx). The sample particle size at this time was set to 425-600 micrometers, and the temperature increase rate was 10 degrees C / min.

Moreover, about the transmittance | permeability of the optical glass of an Example (No.1-No.8), it measured according to Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the presence / absence and degree of coloration of the glass were determined by measuring the transmittance of the glass. 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%).

  In the optical glasses of Examples (No. 1 to No. 8) of the present invention, the difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is 95 ° C. or more, more specifically 97 ° C. As described above, it was revealed that the thermal stability is high. In particular, the optical glasses of Examples (No. 1 to No. 5) of the present invention all have ΔT of 105 ° C. or higher, more specifically 110 ° C. or higher, and Examples (No. 6 to No. 8). It became clear that thermal stability was higher than

As shown in Table 1, the optical glasses of the examples of the present invention all have a λ ₇₀ (wavelength at 70% transmittance) of 500 nm or less, more specifically 454 nm or less, and are difficult to be colored. It became clear. In particular, in the optical glass of Examples (No. 1 to No. 4), it was revealed that λ ₇₀ is 440 nm or less, and that it is more difficult to color compared to Examples (No. 6 to No. 8). .

Each of the optical glasses according to the examples of the present invention has a refractive index (n _d ) of 1.85 or more, more specifically 1.93 or more, and this refractive index (n _d ) is 2.20 or less. Specifically, it was 2.02 or less. For this reason, the refractive index of the optical glass of the Example of this invention was in the desired range.

The optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 10 or more, more specifically 19 or more, and the Abbe number (ν _d ) of 40 or less, more specifically 25. And within the desired range.

Further, as shown in FIG. 2, the optical glass of the example of the present invention has a partial dispersion ratio (θg, F) of (−0.0016 × ν _d +0) in relation to the Abbe number (ν _d ). .6346) or more, more specifically (−0.0016 × ν _d +0.6386) or more, and this partial dispersion ratio (θg, F) is (−0.0058 × ν _d +0.75539) or less, More specifically, it was (−0.0058 × ν _d +0.7509) or less, and was within a desired range.

Therefore, the optical glass of the embodiment of the present invention has high thermal stability, little coloration, and chromatic aberration while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. It became clear that it was small.

  Furthermore, when a precision press-molding preform was formed using the optical glass of the embodiment of the present invention, and the precision press-molding preform was precision press-molded, it could be stably processed into various lens 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 (15)

The glass the total amount of substance of the oxide composition in terms of the mole% in the TeO ₂ component from 10.0 to 95.0%, and optical glass containing 1.0 to 55.0% of GeO ₂ component. The optical glass according to claim 1, wherein a substance amount ratio TeO ₂ / GeO ₂ having an oxide equivalent composition is less than 13.0. Li ₂ O component 0-20.0% and / or Na ₂ O component 0-20.0% and / or K ₂ O component 0-20. 0% and / or Cs ₂ O component from 0 to 20.0%
The optical glass of Claim 1 or 2 which further contains each component of these. MgO component 0 to 15.0% and / or CaO component 0 to 20.0% and / or SrO component 0 to 20.0% and / or BaO in mol% with respect to the total amount of glass in oxide conversion composition Ingredient 0-20.0%
The optical glass according to claim 1, further comprising: 5. The optical glass according to claim 4, wherein the total amount of substances (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) with respect to the total amount of glass having an oxide conversion composition is 5.0% or more and 30.0% or less. ZrO ₂ component 0 to 20.0% and / or Ta ₂ O ₅ component 0 to 20.0% and / or Nb ₂ O ₅ component 0 to 30% by mol% with respect to the total amount of glass in the oxide conversion composition 0.0% and / or La ₂ O ₃ component 0-30.0% and / or Gd ₂ O ₃ component 0-30.0% and / or Y ₂ O ₃ component 0-20.0% and / or Yb ₂ O ₃ component 0 to 20.0% and / or Ga ₂ O ₃ component 0 to 25.0% and / or In ₂ O ₃ component 0 to 25.0% and / or Bi ₂ O ₃ component 0 to 50.0 %
The optical glass according to claim 1, further comprising: Substance amount ratio of oxide conversion composition (TeO ₂ ) / (100-TeO ₂ — (ZrO ₂ + Ta ₂ O ₅ + Nb ₂ O ₅ + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Ga ₂ O ₃ The optical glass according to claim 6, wherein + In ₂ O ₃ + Bi ₂ O ₃ )) is 2.00 or more. ZnO component 0 to 30.0% and / or Al ₂ O ₃ component 0 to 20.0% and / or B ₂ O ₃ component 0 to 50. 0% and / or SiO ₂ component 0-30.0% and / or P ₂ O ₅ component 0-50.0% and / or WO ₃ component 0-25.0% and / or TiO ₂ component 0-30. 0% and / or Sb ₂ O ₃ component 0-1.0% and / or CeO ₂ component 0-1.0%
The optical glass according to claim 1, further comprising: Having 1.85 or more 2.20 or less of the refractive index _{(n d),} 10 or more and 40 or less of the Abbe number ([nu _d) any description of the optical glass of claims 1 to 8 having.   The optical glass according to claim 1, wherein a difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is 95 ° C. or more.   The optical glass according to claim 1, wherein a difference ΔT between the glass transition point (Tg) and the crystallization start temperature (Tx) is 105 ° C. or more. (−0.0016 × ν _d +0.6346) ≦ (θg, F) ≦ (−0...) In a range where the partial dispersion ratio (θg, F) is Abbe number (ν _d ) and ν _d ≦ 25. 0058 × ν _d +0.7539), and in the range of ν _d > 25, (−0.0025 × ν _d +0.6571) ≦ (θg, F) ≦ −0.0020 × ν _d +0.6589 The optical glass according to claim 1, wherein the optical glass satisfies the relationship.   An optical element formed by precision press-molding the optical glass according to claim 1.   A precision press-molding preform comprising the optical glass according to claim 1.   An optical element formed by precision press-molding the precision press-molding preform according to claim 14.

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