JP6062613B2 - Optical glass, preform material and optical element - Google Patents

Description

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

  In recent years, digitization and high definition of devices using optical systems have been rapidly progressing, and various optical devices such as photographing devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions. In this field, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, and to reduce the weight and size of the entire optical system.

Among optical glasses for producing optical elements, in particular, it has a refractive index (n _d ) of 1.75 or more and an Abbe number of 30 or more and 50 or less (which can reduce the weight and size of the entire optical system). There is a great demand for high refractive index, low dispersion glass capable of precision mold pressing with ν _d ). As such a high refractive index and low dispersion glass, glass compositions represented by Patent Documents 1 to 3 are known.

JP 2001-348244 A JP 2008-001551 A JP 2007-063071 A

  The lenses used in the optical system include a spherical lens and an aspheric lens. If an aspheric lens is used, the number of optical elements can be reduced. In addition, various optical elements other than lenses are known which have a complicatedly shaped surface. However, in order to obtain an aspherical surface or a complicatedly shaped surface by conventional grinding and polishing processes, a high-cost and complicated work process is required. Therefore, a method of obtaining a shape of an optical element by directly press-molding a preform material obtained from a gob or a glass block with an ultra-precision processed mold, that is, a method of precision mold press molding is currently mainstream.

  In addition to precision mold press molding of preform materials, grinding and polishing glass moldings obtained by reheating gob or glass block formed from glass material (reheat press molding). A method for obtaining the shape of an optical element is also known.

  However, many of the glasses disclosed in Patent Documents 1 to 3 have low glass transmittance at a visible short wavelength (500 nm or less), and in some cases, they are lightly colored. In particular, a glass having low transmittance at a visible short wavelength is not preferable for use in an optical element that transmits visible light, such as a lens or prism of a camera or projector.

  In addition, the preform material used for precision mold press molding is a method of manufacturing directly from molten glass by a dropping method, a method of grinding and polishing a processed product obtained by reheating a glass block or grinding into a ball shape. It is produced by. In any method, in order to obtain an optical element by forming a molten glass into a desired shape, it is required to reduce devitrification of the formed glass.

The present invention has been made in view of the above problems, and its object is to transmit visible light while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. The object is to obtain an optical glass capable of obtaining a preform material having a high rate and high devitrification resistance.

In order to solve the above-mentioned problems, the present inventors have conducted earnest test research. As a result, in a glass containing a B ₂ O ₃ component and a La ₂ O ₃ component, the inclusion of a TiO ₂ component and an Nb ₂ O ₅ component By reducing the amount, it has been found that the transmittance of glass with respect to visible light can be increased while having a desired refractive index and Abbe number, and the present invention has been completed. Specifically, the present invention provides the following.

(1) the glass the total amount of substance of the oxide composition in terms of, 10.0 to 50.0% of _B 2 _{O 3} component in mole% and the _La 2 _{O 3} component contained 5.0 to 30.0% An optical glass having a molar sum (TiO ₂ + Nb ₂ O ₅ ) of less than 20.0% with respect to the total amount of glass having an oxide equivalent composition.

(2) The optical glass according to (1), wherein a molar sum (TiO ₂ + Nb ₂ O ₅ ) with respect to the total amount of glass having an oxide conversion composition is less than 9.0%.

(3) The TiO ₂ component is less than 0 to less than 20.0% and / or the Nb ₂ O ₅ component is less than 0 to less than 20.0% in mol% with respect to the total amount of glass in the oxide conversion composition (1) or (2) Optical glass as described.

(4) The optical glass according to any one of (1) to (3), wherein the content of the WO ₃ component is 30.0% or less in terms of mol% with respect to the total amount of the glass having an oxide conversion composition.

(5) The optical glass according to (4), wherein the content of the WO ₃ component is 7.0% or more in terms of mol% with respect to the total amount of the glass having an oxide equivalent composition.

  (6) The optical glass according to any one of (1) to (5), wherein the content of the ZnO component is 50.0% or less in terms of mol% with respect to the total amount of the glass having an oxide conversion composition.

  (7) Optical glass as described in (6) whose content of a ZnO component is 38.0% or less by mol% with respect to the glass whole substance amount of an oxide conversion composition.

(8) The optical glass according to any one of (1) to (7), wherein the content of the ZrO ₂ component is 15.0% or less in terms of mol% with respect to the total amount of the glass having an oxide equivalent composition.

(9) The optical glass according to (8), wherein the content of the ZrO ₂ component is less than 3.0% in terms of mol% with respect to the total amount of the glass having an oxide conversion composition.

(10) The optical glass according to any one of (1) to (9), wherein the content of the SiO ₂ component is 25.0% or less in terms of mol% with respect to the total amount of the glass having an oxide conversion composition.

(11) The optical glass according to (10), wherein the content of SiO ₂ component is 3.4% or more by mol% with respect to the total amount of the glass having an oxide conversion composition.

(12) The optical glass according to any one of (1) to (11), wherein a molar sum (SiO ₂ + B ₂ O ₃ ) with respect to the total amount of the glass having an oxide conversion composition is 30.0% or more and 70.0% or less. .

(13) Gd ₂ O ₃ component 0 to 30.0% and / or Y ₂ O ₃ component 0 to 10.0% and / or Yb ₂ O in mol% with respect to the total amount of glass in the oxide equivalent composition ₃ components 0 to 10.0% and / or Lu ₂ O ₃ components 0 to 10.0%
The optical glass according to any one of (1) to (12), further comprising:

(14) The optical glass according to (13), wherein the content of the Gd ₂ O ₃ component is 4.7% or more by mol% with respect to the total amount of the glass having an oxide conversion composition.

(15) The molar 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 amount of glass in the oxide equivalent composition is 10. Optical glass in any one of (1) to (14) which is 0% or more and 40.0% or less.

(16) the glass the total amount of substance of the oxide composition in terms of, 0 to 20.0% Li ₂ O component in mol% and / or Na ₂ O component from 0 to 15.0% and / or _{K 2} O ingredient 0 ~ 10.0%
The optical glass according to any one of (1) to (15), further comprising:

(17) The molar sum of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) with respect to the total amount of glass in an oxide equivalent composition is 20.0% or less. (16) The optical glass as described.

(18) 0 to 10.0% of MgO component and / or 0 to 10.0% of CaO component and / or 0 to 10.0% of SrO component and mol% with respect to the total amount of glass in the oxide conversion composition / Or BaO component 0 to 10.0%
The optical glass according to any one of (1) to (17), further comprising:

  (19) The molar 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 amount of glass in the oxide equivalent composition is 15.0% or less. (18) The optical glass as described.

(20) 0 to 10.0% of GeO ₂ component and / or P ₂ O ₅ component 0 to 10.0% and / or Ta ₂ O ₅ component in mol% with respect to the total amount of glass in the oxide conversion composition 0 to 20.0% and / or _Bi 2 _{O 3} component from 0 to 15.0% and / or TeO ₂ component from 0 to 15.0% and / or _Al 2 _{O 3} component from 0 to 15.0% and / or Ga ₂ O ₃ component 0 to 15.0% and / or Sb ₂ O ₃ component 0 to 1.0%
Each component of
Any one of (1) to (19), wherein the content of F as a substitute for a part or all of one or more oxides of each metal element is 0 to 6.0%. Optical glass.

(21) The optical glass according to any one of (1) to (20), which has a refractive index (n _d ) of 1.75 or more and 1.95 or less and an Abbe number (ν _d ) of 30 or more and 50 or less.

  (22) The optical glass according to any one of (1) to (21), which has a glass transition point (Tg) of 680 ° C. or lower.

  (23) The optical glass according to any one of (1) to (22), which has a liquidus temperature of 1200 ° C. or lower.

  (24) A preform made of the optical glass according to any one of (1) to (23).

  (25) An optical element produced by press-molding the preform material according to (24).

  (26) An optical element having the optical glass according to any one of (1) to (23) as a base material.

  (27) An optical apparatus comprising the optical element according to any one of (25) or (26).

According to the present invention, the desired refractive index and Abbe number can be reduced by reducing the content of TiO ₂ component and Nb ₂ O ₅ component with respect to the glass containing B ₂ O ₃ component and La ₂ O ₃ component. However, the transmittance at a visible short wavelength of the glass is increased. Therefore, it is possible to obtain a preform material that can be preferably used for visible light and has high devitrification resistance while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. Possible optical glasses can be obtained.

In the optical glass of the present invention, the B ₂ O ₃ component is 10.0 to 50.0% and the La ₂ O ₃ component is 5.0 to 30. The molar sum (TiO ₂ + Nb ₂ O ₅ ) is less than 20.0% with respect to the total amount of glass in the oxide equivalent composition. By reducing the content of the TiO ₂ component and the Nb ₂ O ₅ component, the transmittance at a visible short wavelength is increased, and the coloring of the glass is reduced. At the same time, based on the B ₂ O ₃ component and the La ₂ O ₃ component, it has a refractive index (n _d ) of 1.75 or more and 1.95 or less and an Abbe number (ν _d ) of 30 or more and 50 or less. However, the liquidus temperature tends to be low. For this reason, it is possible to obtain a preform material having high devitrification resistance and preferably used for visible light, while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. Optical glass, a preform material and an optical element using the 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 expressed in mol% with respect to the total amount of glass in the oxide equivalent composition. Here, the “oxide equivalent composition” means that the oxide, composite salt, metal fluoride, etc. used as a raw material of the glass component of the present invention are all decomposed and changed into an oxide 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 B ₂ O ₃ component is an essential component that is indispensable as a glass-forming oxide in the optical glass of the present invention containing a large amount of rare earth oxides. In particular, by making the content of the B ₂ O ₃ component 10.0% or more, the devitrification resistance of the glass can be increased and the dispersion of the glass can be reduced. 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 10.0%, more preferably 15.0%, and most preferably 20.0%. On the other hand, by making the content of the B ₂ O ₃ component 50.0% or less, it is possible to easily obtain a larger refractive index and suppress deterioration of chemical durability. Therefore, the upper limit of 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 43.0%. 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 increases the Abbe number of the glass by reducing the dispersion of the glass. In particular, by setting the content of _La 2 _{O 3} component in more than 5.0%, it is possible to increase the refractive index of the glass. 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 5.0%, more preferably 8.0%, and most preferably 10.0%. On the other hand, by setting the content of the La ₂ O ₃ component to 30.0% or less, it is possible to increase the stability of the glass and reduce the devitrification of the glass. Therefore, the La ₂ O ₃ component content is preferably 30.0%, more preferably 25.0%, still more preferably 22.0%, and most preferably 20.30% with respect to the total amount of glass in an oxide equivalent composition. The upper limit is 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.

In the optical glass of the present invention, the molar sum of the TiO ₂ component and the Nb ₂ O ₅ component is preferably less than 20.0%. Thereby, since the devitrification resistance of glass is improved, the optical glass which has a desired optical characteristic can be produced more stably. Therefore, the molar sum of the TiO ₂ component and the Nb ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition is preferably less than 20.0%, more preferably 15.0%, and even more preferably 10.0%. Is the upper limit. Here, in particular, when the molar sum of the TiO ₂ component and the Nb ₂ O ₅ component is less than 9.0%, the transmittance at a visible short wavelength of the glass is increased, and therefore, it is suitably used for applications that transmit visible light. Can be obtained. Therefore, the molar sum of the TiO ₂ component and the Nb ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition, particularly when focusing on the visible light transmittance of the glass, is preferably less than 9.0%, and more The upper limit is preferably 8.0%, and most preferably 7.0%.

TiO ₂ component adjusts the refractive index of the glass and the Abbe number is a component that improves the devitrification resistance, which is an optional component of the optical glass of the present invention. However, when there is too much TiO ₂ , the devitrification resistance is adversely affected, and the transmittance of the glass at a visible short wavelength (500 nm or less) is also deteriorated. Therefore, the content of the TiO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably less than 20.0%, more preferably 15.0%, still more preferably 10.0%, and most preferably Is less than 6.0%. In particular, from the viewpoint of increasing the transmittance for light in the visible region, the content of the TiO ₂ component may be less than 1.0%. TiO ₂ component may be contained in the glass by using as the starting material for example TiO ₂ or the like.

Nb ₂ O ₅ component is a component that raises the refractive index and dispersion of the glass, an optional component of the optical glass of the present invention. In particular, by making the content of the Nb ₂ O ₅ component less than 20.0%, the deterioration of the devitrification resistance of the glass due to the excessive content of the Nb ₂ O ₅ component is suppressed, and the glass transmits visible light. Reduction in rate can be suppressed. Therefore, the content of the Nb ₂ O ₅ component with respect to the total amount of glass in the oxide conversion composition is preferably less than 20.0%, more preferably 15.0%, still more preferably 10.0%, most preferably The upper limit is 5.0%. The Nb ₂ O ₅ component can be contained in the glass using, for example, Nb ₂ O ₅ as a raw material.

The WO ₃ component is a component that increases the refractive index and dispersion of the glass and improves the devitrification resistance of the glass. On the other hand, by setting the content of the WO ₃ component to 30.0% or less, the coloration of the glass can be reduced, and the transmittance in the visible-short wavelength region (less than 500 nm) can be made difficult to decrease. Therefore, the upper limit of the content of the WO ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 30.0%, more preferably 28.0%, and most preferably 25.0%. The optical glass of the present invention it is possible to obtain a glass having desired optical constants and devitrification resistance even without containing WO ₃ components, to contain WO ₃ components or more 7.0% And since the liquidus temperature of glass falls further, the devitrification resistance of glass can further be improved. In addition, the glass transition point can be further lowered while obtaining a high refractive index. Therefore, the content of the WO ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 7.0% as a lower limit, more preferably more than 10.0%, and even more preferably 11.5%. And most preferably more than 15.0%. In particular, from the viewpoint of obtaining a glass having a low glass transition point, the content of the WO ₃ component may be more than 20.0%. The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

The ZnO component is a component that lowers the glass transition temperature (Tg) and improves the chemical durability, and is an optional component in the optical glass of the present invention. However, when a large amount of ZnO component is contained, the devitrification resistance of the glass tends to deteriorate. Therefore, the content of the ZnO component with respect to the total amount of glass having an oxide conversion composition is preferably 50.0%, more preferably 45.0%, and further preferably 40.0%. In particular, from the viewpoint of improving the stability of the glass and lowering the liquidus temperature, the content of the ZnO component with respect to the total amount of glass in the oxide conversion composition is more preferably 38.0% or less, and 27.0. % Or less, and more preferably less than 24.0%. Although it is possible to obtain a glass having desired characteristics even if it does not contain a ZnO component, since the glass transition point is lowered by containing the ZnO component, an optical glass that is easier to press-mold. Easy to obtain. Therefore, the content of the ZnO component with respect to the total amount of glass in the oxide conversion composition is preferably more than 0%, more preferably 3.0%, and most preferably 7.0%. The ZnO component can be contained in the glass using, for example, ZnO, ZnF ₂ or the like as a raw material.

The ZrO ₂ component is a component that contributes to the high refractive index and low dispersion of the glass and improves the devitrification resistance, and is an optional component in the optical glass of the present invention. However, if the amount of ZrO ₂ is too large, the devitrification resistance is deteriorated. Therefore, the content of the ZrO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and even more preferably 5.0%. In particular, from the viewpoint of obtaining an optical glass having a low liquidus temperature and high resistance to devitrification, the content of the ZrO ₂ component with respect to the total amount of the glass in the oxide conversion composition is preferably less than 3.0%, more preferably Is less than 2.5%, most preferably less than 0.5%. 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 SiO ₂ component is a component that increases the viscosity of the molten glass, promotes stable glass formation, and reduces devitrification (generation of crystal) that is not desirable 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, an increase in the glass transition point (Tg) can be suppressed and the high refractive index intended by the present invention can be easily obtained. Accordingly, the content of the SiO ₂ component with respect to the total amount of the glass having an oxide conversion composition is preferably 25.0%, more preferably 20.0%, and most preferably 15.0%. Although the SiO ₂ component is not detrimental technically without containing, by containing a SiO ₂ component, since the liquidus temperature of the glass is lowered, the glass can hardly devitrified. Therefore, the content of the SiO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 0.1%, more preferably 1.0%, and still more preferably 3.4%. In particular, it is most preferable that the SiO ₂ component is contained in an amount of more than 4.0% from the viewpoint that it is difficult to reduce the transmittance at a visible short wavelength of the glass even if the WO ₃ component is contained. 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.

In the optical glass of the present invention, the sum of the contents of the SiO ₂ component and the B ₂ O ₃ component is preferably 30.0% or more and 70.0% or less. By making this sum 30.0% or more, even when the content of the ZrO ₂ component is particularly small, the liquidus temperature of the glass can be lowered to increase the devitrification resistance. Therefore, the sum of the contents of the SiO ₂ component and the B ₂ O ₃ component in the oxide equivalent composition is preferably 30.0%, more preferably 35.0%, and most preferably 37.0%. On the other hand, by setting the sum to 70.0% or less, devitrification due to excessive inclusion of these components can be reduced. Therefore, the sum of the contents of the SiO ₂ component and the B ₂ O ₃ component in the oxide equivalent composition is preferably 70.0%, more preferably 60.0%, and most preferably 50.0%.

In the optical glass of the present invention, the ratio of the content of the SiO ₂ component to the sum of the SiO ₂ component and the B ₂ O ₃ component is preferably 0.10 or more and 0.50 or less. By setting this ratio within a predetermined range, the content of SiO ₂ component that can further increase the transmittance of the glass in the visible short wavelength increases, so an optical glass that is suitably used for light in the visible region is obtained. be able to. Therefore, the molar ratio SiO ₂ / (SiO ₂ + B ₂ O ₃ ) in the oxide equivalent composition is preferably 0.10, more preferably 0.15, and most preferably greater than 0.20. On the other hand, the molar ratio SiO ₂ / (SiO ₂ + B ₂ O ₃ ) in the oxide equivalent composition is preferably 0.50, more preferably 0.45, and most preferably 0.40.

The Gd ₂ O ₃ component is a component that increases the refractive index of the glass and increases the Abbe number, and is an optional component in the optical glass of the present invention. In particular, by making the content of the Gd ₂ O ₃ component 30.0% or less, it becomes easy to obtain a desired optical constant of the glass, and it is possible to suppress an increase in the glass transition point (Tg) and to prevent devitrification of the glass. Can increase the sex. Therefore, the Gd ₂ O ₃ component content is preferably 30.0%, more preferably 20.0%, and most preferably 10.0% with respect to the total amount of glass in the oxide equivalent composition. Incidentally, in the case is not disadvantageous in the art without containing the _Gd 2 _{O 3} component, by replacing a part of _La 2 _{O 3} component _Gd 2 _{O 3} component, not containing _Gd 2 _{O 3} component In comparison, the liquidus temperature of the glass can be lowered, and the devitrification resistance can be further increased. Therefore, the content of the Gd ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably more than 0%, more preferably 1.0%, and even more preferably 3.0%. In particular, from the viewpoint of obtaining a glass having a low liquidus temperature, the content of the Gd ₂ O ₃ component is preferably 4.7% or more. 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, and are optional components in the optical glass of the present invention. In particular, by making the content of the Y ₂ O ₃ component, the Yb ₂ O ₃ component and / or the Lu ₂ O ₃ component 10.0% or less, it becomes easy to obtain a desired optical constant of the glass, and the glass The devitrification resistance can be improved. Therefore, the content of each component of Y ₂ O ₃ , Yb ₂ O _3, and Lu ₂ O ₃ with respect to the total amount of glass in the oxide conversion composition is preferably 10.0%, more preferably 8.0%, Most preferably, the upper limit is 5.0%. Each component of Y ₂ O _{3, Yb} 2 _{O 3} and _Lu 2 _{O 3} is to be contained in the glass by using, for example, _Y 2 _O 3 as a raw _{material, YF 3, Yb 2 O 3} , Lu 2 O 3 , etc. it can.

In the optical glass of the present invention, the molar 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) is 10.0% or more and 40.0. % Or less is preferable. In particular, by making the molar sum of the Ln ₂ O ₃ component 10.0% or more, both the refractive index and the Abbe number of the glass can be increased, so that it is easy to obtain a glass having a desired refractive index and Abbe number. Can do. Accordingly, the lower limit of the molar sum of the Ln ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 10.0%, more preferably 12.0%, and most preferably 15.0%. On the other hand, by making the molar sum of Ln ₂ O ₃ component below 40.0%, because the liquidus temperature of the glass is lowered, thereby reducing the devitrification of the glass. Therefore, the molar sum of the Ln ₂ O ₃ component with respect to the total amount of glass in the oxide conversion composition is preferably 40.0%, more preferably 35.0%, even more preferably 30.0%, and most preferably 25. The upper limit is 0%.

The Li ₂ O component, the Na ₂ O component, and the K ₂ O component are components that improve the meltability of the glass, lower the glass transition point, and increase the devitrification resistance of the glass. Is an optional component. In particular, the Li ₂ O component content is 20.0% or less, the Na ₂ O component content is 15.0% or less, or the K ₂ O component content is 10.0% or less. By making it difficult to lower the refractive index of the glass, the stability of the glass can be increased and the occurrence of devitrification and the like can be reduced. Therefore, the upper limit of the content 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 15.0%, and most preferably 10.0%. Further, the content of the Na ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 5.0%. Further, the content of the K ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The Li ₂ O component, the Na ₂ O component, and the K ₂ O component are, for example, Li ₂ CO ₃ , LiNO ₃ , LiF, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ , K ₂ CO ₃ , KNO as raw materials. ₃ , KF, KHF ₂ , K ₂ SiF ₆ or the like can be used for inclusion in the glass.

The Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is a component that improves the meltability of the glass and reduces the devitrification of the glass. Here, by setting the content of the Rn ₂ O component to 20.0% or less, the refractive index of the glass is hardly lowered, the stability of the glass is increased, and the occurrence of devitrification and the like can be reduced. Therefore, the upper limit of the molar sum of the Rn ₂ O component with respect to the total amount of glass in the oxide conversion composition is preferably 20.0%, more preferably 15.0%, and most preferably 10.0%.

The MgO component, CaO component, SrO component, and BaO component are components that adjust the refractive index, meltability, and devitrification of the glass, and are optional components in the optical glass of the present invention. In particular, by making the content of each of the MgO component, CaO component, SrO component and BaO component 10.0% or less, it becomes easy to obtain a desired refractive index, and loss of glass due to excessive inclusion of these components. The occurrence of see-through can be reduced. Therefore, the content of each of the MgO component, the CaO component, the SrO component, and the BaO component with respect to the total glass material amount of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5. The upper limit is 0%. The MgO component is contained in the glass using, for example, MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) ₂ , BaF _{2 and the} like as raw materials. be able to.

  In the optical glass of the present invention, the total content of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 15.0% or less. Thereby, a desired refractive index can be easily obtained. Therefore, the molar sum of the RO component with respect to the total amount of glass in the oxide conversion composition is preferably 15.0%, more preferably 10.0%, still more preferably 5.0%, and most preferably 2. Less than 0%.

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 the raw material price of GeO ₂ is high, the production cost increases when the amount of GeO ₂ is large, thereby reducing the effect of reducing the Ta ₂ O ₅ component. Therefore, the content of the GeO ₂ component with respect to the total glass material amount of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 1.0%. 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 amount of glass in 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. .

Ta ₂ O ₅ component, while increasing the refractive index of the glass, or to enhance the devitrification resistance of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the Ta ₂ O ₅ component to 20.0% or less, devitrification due to excessive inclusion of the Ta ₂ O ₅ component can be reduced. Moreover, by reducing the content of Ta ₂ O ₅ component is reduced content of expensive Ta ₂ O ₅ component, and since the raw material makes it possible to lower the temperature at which melting of the raw material and the production of optical glass Can reduce the cost. Therefore, the content of the Ta ₂ O ₅ component is preferably 20.0%, more preferably 10.0%, and most preferably 4.5% with respect to the total amount of glass in the oxide equivalent composition. The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

The Bi ₂ O ₃ component is a component that increases the refractive index and decreases the glass transition point (Tg), 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 15.0% or less, an increase in the liquidus temperature can be suppressed, so that a decrease in the devitrification resistance of the glass can be suppressed. 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 15.0%, more preferably less than 10.0%, and most preferably less than 5.0%. And The Bi ₂ O ₃ component can be contained in the glass using, for example, Bi ₂ O ₃ as a raw material.

The TeO ₂ component is a component that raises the refractive index and lowers the glass transition point (Tg), and is an optional component in the optical glass of the present invention. However, TeO ₂ has a problem that it can be alloyed with platinum when melting a glass raw material in a crucible made of platinum or a melting tank in which a portion in contact with molten glass is formed of platinum. Accordingly, the content of the TeO ₂ component with respect to the total amount of glass in the oxide conversion composition is preferably 15.0%, more preferably less than 10.0%, and most preferably less than 5.0%. . The TeO ₂ component can be contained in the glass using, for example, TeO ₂ as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are components that improve the chemical durability of the glass and improve the devitrification resistance of the molten glass, and are optional components in the optical glass of the present invention. In particular, by setting the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 15.0% or less, it is possible to weaken the devitrification tendency of the glass and increase the stability of the glass. Accordingly, the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component with respect to the total amount of the glass having an oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 5. The upper limit is 0%. 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.

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. When the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region is deteriorated. Accordingly, the Sb ₂ O ₃ component content is preferably 1.0%, more preferably 0.7%, and most preferably 0.5% with respect to the total amount of glass in the oxide equivalent composition. 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.

The F component is a component that lowers the glass transition point (Tg) and improves the devitrification resistance while lowering the dispersion of the glass, and is an optional component in the optical glass of the present invention. However, when the content of the F component, that is, the total amount of F substituted for some or all of one or more oxides of each of the above metal elements exceeds 6.0%, Since the volatilization amount of the component increases, it becomes difficult to obtain a stable optical constant, and it becomes difficult to obtain a homogeneous glass. Therefore, the content of the F component with respect to the total amount of glass in the oxide conversion composition is preferably 6.0%, more preferably 5.0%, and most preferably 3.0%. The F component can be contained in the glass by using, for example, ZrF ₄ , AlF ₃ , NaF, CaF ₂ or the like as a raw material.

<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, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding 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. .

Moreover, since lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components with high environmental loads, it is desirable that they are not substantially contained, that is, not contained at all except for inevitable mixing.

  Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has tended to be refrained from being used as a harmful chemical material in recent years, and not only in the glass manufacturing process, but also in the processing process and disposal after commercialization. Until then, environmental measures are required. Therefore, when importance is placed on the environmental impact, it is preferable that these are not substantially contained.

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.
B ₂ O ₃ component from 5.0 to 25.0 wt%, and _La 2 _{O 3} component from 10.0 to 55.0 wt%,
TiO ₂ component 0 to 10.0 mass% and / or Nb ₂ O ₅ component 0 to 35.0 mass% and / or WO ₃ component 0 to 45.0 mass% and / or ZrO ₂ component 0 to 12.0 mass % and / or ZnO component from 0 to 30.0% by weight and / or SiO ₂ component 0 to 10.0% by weight and / or _Gd 2 _{O 3} component from 0 to 55.0% by weight and / or _Y 2 _{O 3} component 0 20.0% by weight and / or _Yb 2 _{O 3} component from 0 to 25.0% by weight and / or _Lu 2 _{O 3} component 0 to 20.0% by weight and / or Li ₂ O component 0 to 5.0 wt% and / or Na ₂ O component from 0 to 8.0 wt% and / or _{K 2} O ingredient from 0 to 8.0 wt% and / or MgO component 0-3.0 wt% and / or CaO component 0-5.0 % By mass and / or SrO component 0-8.0% by mass and / or BaO component 0 0.0% by weight and / or GeO ₂ component from 0 to 7.0% by weight and / or _P 2 _{O 5} component 0 to 10.0% by weight and / or _Ta 2 _{O 5} component from 0 to 30.0% by weight and / or _Bi 2 _{O 3} component from 0 to 40.0% by weight and / or TeO ₂ component from 0 to 15.0% by weight and / or _Al 2 _{O 3} component from 0 to 12.0% by weight and / or _Ga 2 _{O 3} component 0 20.0 wt% and / or _Sb 2 _{O 3} component 0-3.0 wt%
And the total amount as F of the fluoride which substituted a part or all of the 1 type (s) or 2 or more types of said each metal element as 0-3.0 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, the prepared mixture is put into a platinum crucible, and 1100-1500 ° C. in an electric furnace depending on the difficulty of melting the glass composition. It is produced by melting in the temperature range of 2 to 5 hours, stirring and homogenizing, 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 (n _d ) and low dispersibility. In particular, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.75, more preferably 1.77, and most preferably 1.80, preferably 1.95, more preferably 1.95. 92, most preferably 1.90. Further, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 30, more preferably 32, most preferably 33, the lower limit, preferably 50, more preferably 45, most preferably 40. . 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, 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 450 nm or less, more preferably 430 nm or less, and most preferably. Is 410 nm or less. Further, the wavelength (λ ₅ ) exhibiting a spectral transmittance of 5% is 400 nm or less, more preferably 380 nm or less, and most preferably 370 nm or less. In addition, the wavelength (λ ₈₀ ) exhibiting a spectral transmittance of 80% is 500 nm or less, more preferably 480 nm or less, and most preferably 470 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 preferably used as a material for an optical element such as a lens.

  The optical glass of the present invention preferably has high devitrification resistance. In particular, the optical glass of the present invention preferably has a low liquidus temperature of 1200 ° C. or lower. More specifically, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1200 ° C, more preferably 1100 ° C, and most preferably 1040 ° C. As a result, even if the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that the devitrification resistance when the glass is formed from the molten state can be increased. The influence on the optical characteristics of the optical element can be reduced. Moreover, since the range of the temperature at which the preform material can be stably produced is widened, the preform material can be formed even when the melting temperature of the glass is lowered, and the energy consumed when forming the preform material can be suppressed. On the other hand, the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited, but the liquidus temperature of the glass obtained by the present invention is approximately 500 ° C. or higher, specifically 550 ° C. or higher, more specifically 600. Often above ℃. In this specification, “liquid phase temperature” means that a 30 cc cullet-like glass sample is put into a platinum crucible in a platinum crucible having a capacity of 50 ml and completely melted at 1250 ° C., and the temperature is lowered to a predetermined temperature. Then, the glass surface and the presence or absence of crystals in the glass are observed immediately after taking out of the furnace and cooling to indicate the lowest temperature at which no crystals are observed. Here, the predetermined temperature represents a temperature set in increments of 20 ° C. from 1180 ° C. to 1000 ° C.

  The optical glass of the present invention has a glass transition point (Tg) of 680 ° C. or lower. Thereby, since glass softens at a lower temperature, it can be easily press-molded at a lower temperature. In addition, it is possible to extend the life of the mold by reducing oxidation of the mold used for press molding. Therefore, the upper limit of the glass transition point (Tg) of the optical glass of the present invention is preferably 680 ° C., more preferably 650 ° C., further preferably 620 ° C., and most preferably 595 ° 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 optical glass of the present invention preferably has a yield point (At) of 720 ° C. or lower. Like the glass transition point (Tg), the yield point (At) is one of indices indicating the softening property of glass, and is an index indicating a temperature close to the press molding temperature. Therefore, by using a glass having a yield point (At) of 720 ° C. or lower, press molding at a lower temperature becomes possible, so that press molding can be performed more easily. Accordingly, the yield point (At) of the optical glass of the present invention is preferably 720 ° C, more preferably 700 ° C, and most preferably 680 ° C. The lower limit of the yield point (At) of the optical glass of the present invention is not particularly limited, but the yield point (At) of the glass obtained by the present invention is generally 150 ° C. or higher, specifically 200 ° C. or higher, more specifically. Specifically, it is often 250 ° C. or higher.

The optical glass of the present invention preferably has a low partial dispersion ratio (θg, F). More specifically, the partial dispersion ratio (θg, F) of the optical glass of the present invention is (−2.50 × 10 ⁻³ × ν _d +0.6571) ≦ with respect to the Abbe number (ν _d ) ≦ The relationship (θg, F) ≦ (−2.50 × 10 ⁻³ × ν _d +0.6971) is satisfied. As a result, an optical glass having a partial dispersion ratio (θg, F) close to the normal line can be obtained, so that chromatic aberration of an optical element formed from the optical glass can be reduced. The partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably (−2.50 × 10 ⁻³ × ν _d +0.6571), more preferably (−2.50 × 10 ⁻³ × ν _d). +0.6591), and most preferably, (-2.50 × 10 ⁻³ × ν _d +0.6611) is the lower limit. On the other hand, the partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably (−2.50 × 10 ⁻³ × ν _d +0.6971), more preferably (−2.50 × 10 ^−3). × ν _d +0.6921), most preferably (−2.50 × 10 ⁻³ × ν _d +0.6871) is set as the upper limit.

[Preform materials 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 was prepared from optical glass, and after performing reheat press molding on this preform, polishing was performed to prepare a glass molded body, or polishing was performed. It is possible to produce a glass molded body by performing precision press molding on a preform, or a preform molded by a known floating molding or the like. In addition, the means for producing the glass molded body is not limited to these means.

  As described above, the optical glass of the present invention is useful for various optical elements and optical designs. In particular, a preform material is formed from the optical glass of the present invention, and a reheat press is performed using the preform material. It is preferable to fabricate an optical element such as a lens or a prism by molding or precision press molding. This makes it possible to form a preform material with a large diameter, so that the optical elements can be enlarged, but the imaging characteristics and projection can be performed with high definition and high accuracy when used in optical devices such as cameras and projectors. The characteristics can be realized.

Compositions of Examples (No. 1 to No. 27), Reference Examples (No. A) and Comparative Examples (No. A) of the present invention, and refractive indexes (nd) and Abbe numbers (νd) of these glasses , Partial dispersion ratio (θg, F), glass transition point (Tg), yield point (At), liquidus temperature, wavelength exhibiting spectral transmittance of 5%, 70% and 80% (λ ₅ , λ ₇₀ and λ ₈₀ ) are shown in Tables 1 to 4. Among these, Examples (No. 1-2, 12-13, 21-22, 25-27) are reference examples of the present invention. The following examples are merely for illustrative purposes, and are not limited to these examples.

  The glass of Examples (No. 1 to No. 27), Reference Example (No. A), and Comparative Example (No. A) of the present invention are oxides and hydroxides corresponding to the raw materials of the respective components. High purity raw materials used for ordinary optical glass such as carbonate, nitrate, fluoride, hydroxide, and metaphosphoric acid compound are selected, and the composition ratios of the respective examples shown in Tables 1 to 4 are obtained. After being weighed and mixed uniformly, the mixture was put into a platinum crucible, melted in a temperature range of 1100 to 1500 ° C. for 2 to 5 hours in an electric furnace according to the melting difficulty of the glass composition, and then stirred and homogenized. The glass was cast into a mold or the like and slowly cooled to produce a glass.

Here, the refractive index (n _d ), Abbe number (ν _d ) and partial dispersion of the glasses of Examples (No. 1 to No. 27), Reference Examples (No. A) and Comparative Examples (No. A). The ratio (θg, F) was measured based on Japan Optical Glass Industry Association Standard JOGIS01-2003. Then, with respect to the obtained Abbe number (ν _d ) and partial dispersion ratio (θg, F), the intercept when the slope a is 0.0025 in the relational expression (θg, F) = − a × ν _d + b b was determined. Here, the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio (θg, F) are measured by measuring the glass obtained at a slow cooling rate of -25 ° C./hr. Asked.

  Moreover, the glass transition point (Tg) and the yield point (At) of the glass of an Example (No.1-No.27), a reference example (No.A), and a comparative example (No.A) are horizontal type | mold expansion measurements. It was determined by performing measurement using a vessel. Here, the sample at the time of measuring used the thing of (phi) 4.8mm and length 50-55mm, and the temperature increase rate was 4 degrees C / min.

Moreover, the transmittance | permeability of the glass of an Example (No.1-No.27), a reference example (No.A), and a comparative example (No.A) was 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. More 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 ₅ (wavelength when the transmittance was 5%), λ ₇₀ (transmittance). The wavelength at 70%) and λ ₈₀ (wavelength at 80% transmittance) were determined.

  Moreover, the liquidus temperature of the glass of an Example (No.1-No.27), a reference example (No.A), and a comparative example (No.A) is 30 cc cullet-like in a platinum crucible with a capacity of 50 ml. After putting the glass sample in a platinum crucible and completely melting at 1250 ° C., the temperature is lowered to any temperature set in increments of 20 ° C. from 1180 ° C. to 1000 ° C., held for 12 hours, taken out of the furnace and cooled The glass surface and the presence or absence of crystals in the glass were immediately observed to determine the lowest temperature at which no crystals were observed.

As shown in Tables 1 to 4, all of the optical glasses of the examples of the present invention had a λ ₇₀ (wavelength at a transmittance of 70%) of 450 nm or less, more specifically 410 nm or less. In addition, in the optical glasses of the examples of the present invention, each of λ ₅ (wavelength when the transmittance was 5%) was 400 nm or less, more specifically 360 nm or less. In addition, in the optical glasses of the examples of the present invention, λ ₈₀ (wavelength at 80% transmittance) was 500 nm or less, and more specifically, 460 nm or less. For this reason, it became clear that the optical glass of the Example of this invention has the high transmittance | permeability in a visible short wavelength, and is hard to color. On the other hand, in the glass of the comparative example (No. A) of the present invention, λ ₇₀ was higher than 450 nm. In the glass of Reference Example (No. A) of the present invention, λ ₈₀ was higher than 510 nm. As described above, the reason why λ ₈₀ , λ ₇₀ , and λ ₅ are different is that the optical glass of the example of the present invention has a TiO ₂ component and Nb ₂ more than the reference example (No. A) and the comparative example (No. A). It is conceivable that the content of the O ₅ component is small. That is, in the optical glass of the example of the present invention, λ ₈₀ , λ ₇₀ , and λ ₅ are reference examples (No. A) because of the low content of TiO ₂ component and Nb ₂ O ₅ component. It is guessed that it is lower than that of Comparative Example (No. A).

In addition, the optical glasses of the examples of the present invention all had a liquidus temperature of 1200 ° C. or lower, more specifically 1040 ° C. or lower, and were within a desired range. On the other hand, the glass of the reference example (No. A) of the present invention had a liquidus temperature of 1060 ° C. The reason why the liquidus temperature is so low is that the optical glass of the examples of the present invention has a _high content of the WO ₃ component and a low content of the ZrO ₂ component. For this reason, it became clear that the optical glass of the Example of this invention has low liquidus temperature.

  The optical glasses of the examples of the present invention all had a glass transition point (Tg) of 680 ° C. or lower, more specifically 630 ° C. or lower, and were within a desired range. Further, the optical glass of Example (No. 8) of the present invention had a yield point (At) of 720 ° C. or less, more specifically 680 ° C. or less, and was within a desired range.

The optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.75 or more, more specifically 1.85 or more, and this refractive index (n _d ) is 1.95 or less. More specifically, it was 1.90 or less, and was within a desired range.

The optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 30 or more, more specifically 33 or more, and the Abbe number (ν _d ) of 50 or less, more specifically 40. And within the desired range.

Further, the optical glasses of the examples of the present invention all have a partial dispersion ratio (θg, F) of (−2.50 × 10 ⁻³ × ν _d +0.6571) or more, more specifically (−2.50). × 10 ⁻³ × ν _d +0.6706) or more. In the other hand, the partial dispersion ratio of the optical glass of the embodiment of the present ^{invention, (- 2.50 × 10 -3 ×} ν d +0.6971) or less, and more (-2.50 × ^{10 -3} × (ν _d +0.6745) or less. Therefore, it was found that these partial dispersion ratios (θg, F) are within a desired range.

Therefore, the optical glass of the example of the present invention has high transmittance at a visible short wavelength and high devitrification resistance, while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. And it became clear that it is easy to perform press molding by heat softening.

  Furthermore, using the optical glass of 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 into the shape of a lens and a prism. 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 (12)

The glass the total amount of substance of the oxide composition in terms of, 20.0 to 41.531% of _B 2 _{O 3} component in mole%,
10.0 to 30.0% of La ₂ O ₃ component,
4.7 to 20.0% of Gd ₂ O ₃ component,
7.0 to 30.0% of WO ₃ component,
A ZnO component of 3.0 to less than 24.0% (excluding those containing 22% or more) and a ZrO ₂ component of more than 0% and 15.0% or less,
The content of the Li ₂ O component is 2.096% or less,
The molar sum (TiO ₂ + Nb ₂ O ₅ ) with respect to the total amount of glass in the oxide equivalent composition is less than 20.0%,
The molar sum (SiO ₂ + B ₂ O ₃ ) with respect to the total amount of glass in the oxide conversion composition is 30.0% or more and 50.0% or less,
A wavelength (λ ₇₀ ) having a refractive index (n _d ) of 1.78881 or more and 1.95 or less, an Abbe number (ν _d ) of 30 or more and 50 or less, and a spectral transmittance of 70% in a sample having a thickness of 10 mm. Is an optical glass having a liquidus temperature of 1200 ° C. or lower. _2. The optical glass according to claim 1, wherein the TiO ₂ component is less than 0 to less than 20.0% and the Nb ₂ O ₅ component is less than 0 to less than 20.0% in terms of mol% with respect to the total amount of glass in an oxide conversion composition. 3. The optical glass according to claim 1, wherein a molar sum (TiO ₂ + Nb ₂ O ₅ ) with respect to the total amount of the glass having an oxide conversion composition is less than 9.0%. SiO ₂ component 0 to 25.0% in mol% with respect to the total amount of glass in oxide conversion composition,
Y ₂ O ₃ component 0 to 10.0%,
Yb ₂ O ₃ component 0 to 10.0%,
Lu ₂ O ₃ component 0 to 10.0%
Na ₂ O component 0 to 15.0%,
K ₂ O component 0 to 10.0%
MgO component 0 to 10.0%,
CaO component 0 to 10.0%,
SrO component 0 to 10.0%,
BaO component 0 to 10.0%
GeO ₂ component 0 to 10.0%,
P ₂ O ₅ component 0 to 10.0%,
Ta ₂ O ₅ component 0 to 20.0%,
Bi ₂ O ₃ component 0 to 15.0%,
TeO ₂ component 0 to 15.0%,
Al ₂ O ₃ component 0 to 15.0%,
Ga ₂ O ₃ component 0 to 15.0% and Sb ₂ O ₃ component 0 to 1.0%
And
The content as F of the fluoride substituted with one or more oxides of one or more of the above metal elements is 0 to 6.0%.
The optical glass according to any one of claims 1 to 3. 5. The optical glass according to claim 4, wherein the content of SiO ₂ component is 3.4% or more by mol% with respect to the total amount of the glass having an oxide conversion composition. The molar 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 amount of glass in an oxide equivalent composition is 14.7 % or more The optical glass according to any one of claims 1 to 5, which is 40.0% or less. _2. The molar sum of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) with respect to the total amount of glass having an oxide equivalent composition is 20.0% or less. The optical glass according to any one of 6 to 6.   2. The molar sum of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) with respect to the total amount of glass having an oxide equivalent composition is 15.0% or less. 8. The optical glass according to any one of 7 to 7.   The optical glass according to any one of claims 1 to 8, which has a glass transition point (Tg) of 680 ° C or lower.   A preform material comprising the optical glass according to claim 1.   An optical element using the optical glass according to claim 1 as a base material. Claim 1 1 Symbol mounting optical apparatus equipped with the optical element.