JP2011230992A - Optical glass, preform material and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass which has a little striae and hardly causes devitrification even though the refractive index (n) and Abbe number (ν) are each within a desired range, and from which a preform material having a large-diameter is formed, and to provide a preform material and an optical element each using the optical glass.SOLUTION: The optical glass contains, by mass% based on the total mass of the glass having a composition in terms of oxide, 5.0-35.0% of a BOcomponent, 15.0-50.0% of a LaOcomponent, and 1.0-25.0% of WOcomponent, wherein the content of LiO component is ≤5.0%.

Description

  The present invention relates to an optical glass, a preform material, and an optical element having a low glass transition temperature (Tg) and a high refractive index and high dispersibility.

  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 and 2 are known.

JP 2006-016293 A JP 2006-016295 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 the method of precision mold press molding a preform material, a glass molded body obtained by reheating and molding (reheat press molding) a gob or glass block formed from a glass material is ground and polished. Methods are also known.

  As a manufacturing method of a preform material used for such precision mold press molding and reheat press molding, a method of directly manufacturing from molten glass by a dropping method, a glass block was reheat pressed or obtained by grinding into a ball shape. It is produced by a method of grinding and polishing a workpiece. In any method, it is required to reduce striae and devitrification of the formed glass in order to obtain an optical element by molding the molten glass into a desired shape. However, the glasses disclosed in Patent Documents 1 and 2 have a problem of causing quality defects such as striae and devitrification, particularly when forming a preform material having a large diameter.

The present invention has been made in view of the above-described problems, and the object of the present invention is to reduce the striae while the refractive index (n _d ) and the Abbe number (ν _d ) are within the desired ranges. It is to obtain an optical glass that can form a preform material having a large diameter, and a preform material and an optical element using the same.

In order to solve the above-mentioned problems, the present inventors have conducted intensive test studies. As a result, the B ₂ O ₃ component, the La ₂ O ₃ component, and the WO ₃ component are used together, and the content of the Li ₂ O component It is found that the refractive index and the Abbe number of the glass are adjusted by suppressing the refractive index within a predetermined range, the liquidus temperature of the glass is lowered, and the viscosity at the liquidus temperature of the glass is appropriately increased. It came to complete. Specifically, the present invention provides the following.

(1) 5.0 to 35.0% of B ₂ O ₃ component, 15.0 to 50.0% of La ₂ O ₃ component, and WO _three components containing 1.0 to 25.0%, optical glass content of Li ₂ O component is less than 5.0%.

(2) Gd ₂ O ₃ component 0 to 30.0% and / or Y ₂ O ₃ component 0 to 15.0% and / or Yb ₂ O _{3 in} mass% with respect to the total glass mass of the oxide equivalent composition. components from 0 to 15.0% and / or _Lu 2 _{O 3} component from 0 to 10.0%
The optical glass according to (1), further comprising:

(3) The mass sum of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) with respect to the total glass mass of the oxide equivalent composition is 20.0. % Or more and 60.0% or less of the optical glass according to (1) or (2).

(4) The mass ratio La ₂ O ₃ / (Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ ) of the oxide equivalent composition is 1.50 or more and 15.00 or less (2) or (3 ) Optical glass as described.

(5) The optical glass according to any one of (1) to (4), further containing 25.0% or less of Ta ₂ O ₅ component by mass% with respect to the total glass mass of the oxide equivalent composition.

(6) the entire mass of the glass in terms of oxide composition is the content of _Ta 2 _{O 5} component in weight percent 1.0% or more (5), wherein the optical glass.

  (7) Optical glass in any one of (1) to (6) whose content of a ZnO component is 40.0% or less by mass% with respect to the glass total mass of an oxide conversion composition.

  (8) The optical glass according to (7), wherein the content of the ZnO component is less than 14.0% by mass% with respect to the total glass mass of the oxide equivalent composition.

  (9) The optical glass according to (7), wherein the content of the ZnO component is 14.0% or more by mass% with respect to the total glass mass of the oxide equivalent composition.

(10) Na ₂ O component 0 to 10.0% and / or K ₂ O component 0 to 10.0% in terms of mass% with respect to the total glass mass of the oxide equivalent composition.
The optical glass according to any one of (1) to (9), further comprising:

(11) The mass 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 glass mass of the oxide equivalent composition is 10.0% or less ( The optical glass according to any one of 1) to (10).

(12) Each component of SiO ₂ component 0 to 15.0% and / or Nb ₂ O ₅ component 0 to less than 10.0% is further contained in mass% with respect to the total glass mass of the oxide equivalent composition ( The optical glass according to any one of 1) to (11).

(13) The mass ratio (Rn ₂ O + La ₂ O ₃ + Gd ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ ) of the oxide equivalent composition is 0.59 or more and 3.00 or less. The optical glass according to (12).

(14) 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 / Or BaO component 0 to 10.0%
The optical glass according to any one of (1) to (13), further comprising:

  (15) The mass sum of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) with respect to the total glass mass of the oxide equivalent composition is 10.0% or less ( 14) Optical glass as described.

(16) P ₂ O ₅ component 0 to 10.0% and / or GeO ₂ component 0 to 10.0% and / or Al ₂ O ₃ component 0% by mass with respect to the total glass mass of the oxide equivalent composition 0 10.0% and / or a ZrO ₂ component from 0 to 10.0% and / or TiO ₂ component from 0 to 10.0% and / or _Bi 2 _{O 3} component from 0 to 20.0% and / or TeO ₂ component 0 to 20.0% and / or Sb ₂ O ₃ component 0 to 1.0%
Each component of
Any one of (1) to (15), wherein the content of fluoride in which one or more of the above metal elements are partially or entirely substituted with fluoride is 0 to 6.0%. Optical glass.

(17) The optical glass according to any one of (1) to (16), 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.

  (18) The optical glass according to any one of (1) to (17), which has a glass transition point (Tg) of 680 ° C. or lower.

  (19) The optical glass according to any one of (1) to (18), which has a liquidus temperature of 1250 ° C. or lower.

  (20) A preform made of the optical glass according to any one of (1) to (19).

  (21) An optical element produced by press-molding the preform material according to (20).

  (22) An optical element having the optical glass according to any one of (1) to (19) as a base material.

  (23) An optical apparatus comprising the optical element according to any one of (21) and (22).

According to the present invention, the B ₂ O ₃ component, the La ₂ O ₃ component, and the WO ₃ component are used in combination, and the content of the Li ₂ O component is suppressed within a predetermined range, whereby the refractive index and the Abbe of the glass are reduced. As the number is adjusted, the liquidus temperature of the glass is lowered and the viscosity at the liquidus temperature of the glass is moderately increased. For this reason, a preform material having both a small striae and difficulty of devitrification and having a large diameter is formed while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. Is possible.

  Next, the reason why the composition range of each component is limited as described above in the optical glass of the present invention will be described. In the present specification, unless otherwise specified, the content of each component is expressed in mass%.

The optical glass of the present invention, the entire mass of the glass in terms of oxide composition, 5.0 to 35.0% of _B 2 _{O 3} component in mass%, a _La 2 _{O 3} component from 15.0 to 50.0 %, And WO ₃ component is contained in an amount of 1.0 to 25.0%, and the content of the Li ₂ O component is 5.0% or less. Thus, by adding the WO ₃ ingredient within the above range, the viscosity at the liquidus temperature of the glass is moderately increased. Moreover, by suppressing the content of the Li ₂ O component within the above range, a glass material having a low glass transition point (Tg) can be obtained while maintaining devitrification resistance. At the same time, an alkali metal component is preferably used in combination with the B ₂ O ₃ component, La ₂ O ₃ component and WO ₃ component, and the content of these components is kept within the above range, whereby the refractive index and the Abbe number of the glass are increased. Is adjusted, and the liquidus temperature of the glass is lowered. Therefore, while having a refractive index (n _d ) of 1.75 or more and an Abbe number (ν _d ) of 30 or more, the diameter is large, and press molding by heat softening is easy, and striae and devitrification are reduced. An optical glass capable of forming the preform material, and 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 mass% with respect to the total mass of the glass in terms of oxide. 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 mass of the said production | generation oxide into 100 mass%.

<About essential and optional components>
The B ₂ O ₃ component is an essential component indispensable as a glass-forming oxide in the optical glass of the present invention containing a large amount of rare earth oxide. In particular, by setting the content ratio of the B ₂ O ₃ component to 5.0% or more, the devitrification resistance of the glass can be increased and the dispersion of the glass can be reduced. On the other hand, by making the content ratio of the B ₂ O ₃ component 35.0% or less, it is possible to easily obtain a larger refractive index and suppress deterioration of chemical durability. Therefore, the content ratio of the B ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%, more preferably 8.0%, still more preferably 10.0%, and most preferably 11.0. % Is the lower limit, preferably 35.0%, more preferably 30.0%, still more preferably 25.0%, and most preferably 20.0%. 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 an amount of 15.0% or more, it is possible to increase the refractive index of the glass. On the other hand, by setting the content of La ₂ O ₃ component below 50.0%, it can be reduced devitrification of the glass and lower the liquidus temperature of the glass. Therefore, the content of the La ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 20.0%, still more preferably 25.0%, and most preferably 28.5. % Is the lower limit, preferably 50.0%, more preferably 48.0%, even more preferably 45.0%, and most preferably 43.0%. 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.

The WO ₃ component is a component that adjusts the refractive index and dispersion of the glass and improves the devitrification resistance of the glass. In particular, by making the content of the WO ₃ component 1.0% or more, an effect of lowering the liquidus temperature of the glass can be obtained, so that the devitrification resistance of the glass can be improved. Moreover, since the viscosity at the liquidus temperature of the molten glass is increased, a preform material having a large diameter can be easily obtained. Moreover, the glass transition point of glass can be made low. On the other hand, by setting the content of the WO ₃ component to 25.0% or less, the coloring 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. Accordingly, the content of the WO ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 2.0%, and most preferably 2.5%, and preferably 25.0. %, More preferably 15.0%, still more preferably 12.0%, and most preferably 10.0%. The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

Li 2 _O component, as well as improving the meltability of the glass is a component that reduces the devitrification of the glass, an optional component of the optical glass of the present invention. However, when the Li ₂ O component is excessively contained, the glass tends to be devitrified. Therefore, the content of the Li ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%, more preferably 3.0%, and most preferably 2.0%. 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 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 setting the content of the Gd ₂ O ₃ component to 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 loss of the glass. Permeability can be increased. Accordingly, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 30.0%, more preferably 20.0%, still more preferably 15.0%, most preferably 10. The upper limit is 0%. Although there is no technical disadvantage even if the Gd ₂ O ₃ component is not contained, it is easy to obtain a desired optical constant because the refractive index and the Abbe number of the glass are increased by containing 1.0% or more. it can. Therefore, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 2.0%, and most preferably 2.5%. 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, the Y ₂ O ₃ component content and the Yb ₂ O ₃ component content are each 15.0% or less, and the Lu ₂ O ₃ component content is 10.0% or less. The number can be easily obtained, and the devitrification resistance of the glass can be increased. Therefore, the content of each component of Y ₂ O ₃ and Yb ₂ O ₃ with respect to the total glass mass of the oxide-converted composition is preferably 15.0%, more preferably 10.0%, and most preferably 5.0. % Is the upper limit. The content of the Lu ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. Each component of Y ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ should be contained in the glass using, for example, Y ₂ O ₃ , YF ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ or the like as a raw material. Can do.

In the optical glass of the present invention, the mass sum of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 20.0% or more and 60.0. % Or less is preferable. In particular, when the mass sum of the Ln ₂ O ₃ component is 20.0% or more, the refractive index and the Abbe number of the glass are increased, so that a desired optical constant can be easily obtained. On the other hand, when the mass sum of the Ln ₂ O ₃ component is 60.0% or less, the devitrification resistance of the glass can be enhanced while suppressing an increase in the glass transition point (Tg). Therefore, the mass sum of the Ln ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 20.0%, more preferably 30.0%, most preferably 35.0%, and preferably 60%. 0.0%, more preferably 55.0%, and most preferably 50.0%.

Further, the optical glass of the present invention, _Gd 2 _{O 3 component,} Y 2 _{O 3} component, to one or more mass sum is selected from the group consisting of _Yb 2 _{O 3} component and _Lu 2 _{O 3} component, _La 2 O The content ratio of the _three components is preferably 1.50 or more and 15.00 or less. By setting this ratio to 1.50 or more, among the above-mentioned Ln ₂ O ₃ components, the content of the La ₂ O ₃ component, which has a small effect of deteriorating the stability of the glass, increases, so that a high refractive index and low dispersion While maintaining the above, the liquidus temperature of the glass can be lowered and the devitrification resistance can be increased. On the other hand, by setting this ratio to 15.00 or less, the liquidus temperature of the glass is lowered by effectively adding a plurality of rare earth elements, so that the devitrification resistance of the glass can be improved. Therefore, the mass ratio La ₂ O ₃ / (Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ ) of the oxide equivalent composition is preferably 1.50, more preferably 1.80, most preferably The lower limit is 2.00, preferably 15.00, more preferably 14.00, and most preferably 10.00.

Ta ₂ O ₅ component increases 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 25.0% or less, deterioration of the devitrification resistance of the glass due to excessive inclusion of the Ta ₂ O ₅ component can be suppressed. Therefore, the content of the Ta ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 25.0%, more preferably 23.0%, and most preferably 21.0%. Although there is no technical disadvantage even if the Ta ₂ O ₅ component is not contained, the viscosity at a high temperature of the molten glass can be increased by containing 1.0% or more. Moreover, since the transmittance | permeability (for example, the value of (lambda) ₅ ) of glass is raised, transparency with respect to visible light of glass can be improved. Therefore, the content ratio of the Ta ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 1.0%, more preferably 5.0%, and most preferably 7.5%. The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

The ZnO component is a component that has a large effect of lowering the glass transition temperature (Tg) and has an effect of improving chemical durability, and is an optional component in the optical glass of the present invention. However, when there is too much content of a ZnO component, the devitrification resistance of glass will deteriorate easily. Therefore, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably 40.0%, more preferably 35.0%, and most preferably 30.0%. The ZnO component can be contained in the glass using, for example, ZnO, ZnF ₂ or the like as a raw material.

  Here, in particular, by setting the content of the ZnO component to less than 14.0%, it is possible to easily obtain a glass having a high refractive index and a low dispersion and having a high devitrification resistance. Therefore, particularly from the viewpoint of achieving both high refractive index and low dispersion and devitrification resistance, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably less than 14.0%, more preferably The upper limit is less than 11.0%, and most preferably 9.0%.

  On the other hand, in particular, by setting the content of the ZnO component to 14.0% or more, a glass having a lower glass transition temperature (Tg) and higher transparency to visible light can be obtained. Therefore, from the viewpoint of realizing a particularly low glass transition temperature (Tg) and high transparency to visible light, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably 14.0%, more preferably The upper limit is 15.2%, and most preferably 17.0%.

  Although it is possible to obtain a glass having desired characteristics even if it does not contain a ZnO component, since the liquidus temperature of the glass is lowered by containing the ZnO component, the devitrification resistance of the glass is reduced. Can be increased. Moreover, since the glass transition point becomes low, it is easy to obtain an optical glass that is easy to press-mold. Therefore, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably 0.1%, more preferably 0.5%, and most preferably 1.0%.

The Na ₂ O component is a component that improves the meltability of the glass, lowers the glass transition point, and increases the devitrification resistance of the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of the Na ₂ O component 10.0% or less, it is difficult to lower the refractive index of the glass, and the liquidus temperature of the glass can be lowered to reduce the occurrence of devitrification and the like. . Therefore, the content of the Na ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The 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 improves the meltability of the glass, lowers the glass transition point, and adjusts the refractive index and Abbe number of the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of the K ₂ O component 10.0% or less, it is difficult to lower the refractive index of the glass, and the liquidus temperature of the glass can be lowered to reduce the occurrence of devitrification and the like. . Therefore, the content of the K ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The 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 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 making the content of the Rn ₂ O component 10.0% or less, it is difficult to lower the refractive index of the glass, and the liquidus temperature of the glass is lowered to reduce the occurrence of devitrification and the like. it can. Therefore, the upper limit of the mass sum of the Rn ₂ O component with respect to the total mass of the glass in oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%.

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 15.0% or less, an increase in the glass transition point (Tg) can be suppressed and the refractive index intended by the present invention can be easily obtained. Therefore, the content of the SiO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 12.0%, and most preferably 10.0%. Although there is no technical disadvantage even if the SiO ₂ component is not contained, the liquid phase temperature of the glass is increased by containing 0.1% or more, and thus the glass can be made more difficult to devitrify. Therefore, the content of the SiO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 0.1%, more preferably 1.0%, more preferably 1.5%, and most preferably 2.0%. The lower limit. 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.

Nb ₂ O ₅ component increases the refractive index of the glass is a component to improve the devitrification resistance, which is 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 10.0%, 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 transmittance of the glass to visible light is reduced. The decrease can be suppressed. Therefore, the content of the Nb ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably less than 10.0%, more preferably less than 8.0%, and most preferably less than 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 optical glass of the present invention is composed of SiO ₂ component, B ₂ O ₃ component, Ta ₂ O with respect to one or more kinds of mass sum selected from the group consisting of Rn ₂ O component, La ₂ O ₃ component and Gd ₂ O _3. The ratio of one or more mass sums selected from the group consisting of ₅ components, WO ₃ components and Nb ₂ O ₅ components is preferably 0.59 or more and 3.00 or less. By setting this ratio within the range of 0.59 or more and 3.00 or less, the liquidus temperature of the glass is lowered, so that the devitrification resistance of the glass can be improved. Therefore, the mass ratio (Rn ₂ O + La ₂ O ₃ + Gd ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ ) of the oxide equivalent composition is preferably 0.59, more preferably Is 0.80, most preferably 0.90. The mass ratio is preferably 3.00, more preferably 2.50, and most preferably 2.00.

The MgO component is a component that adjusts the refractive index of the glass, and is an optional component in the optical glass of the present invention. In particular, by making the content of the MgO component 10.0% or less, a desired refractive index can be easily obtained, and the occurrence of devitrification of the glass can be reduced. Therefore, the content of the MgO component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The 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 meltability of glass, and is an arbitrary component in the optical glass of this invention. In particular, by making the content of the CaO component 10.0% or less, it is possible to easily obtain a desired refractive index and reduce the devitrification of the glass. Therefore, the content of the CaO component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The CaO component can be contained in the glass using, for example, CaCO ₃ , CaF ₂ or the like as a raw material.

A SrO component is a component which adjusts the refractive index of glass and improves the devitrification property of glass, and is an arbitrary component in the optical glass of this invention. In particular, the desired refractive index can be easily obtained by setting the content of the SrO component to 10.0% or less. Therefore, the content of the SrO component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The SrO component can be contained in the glass using, for example, Sr (NO ₃ ) ₂ , SrF ₂ or the like as a raw material.

A BaO component is a component which adjusts the refractive index of glass and improves the devitrification property of glass, and is an arbitrary component in the optical glass of this invention. In particular, the desired refractive index can be easily obtained by setting the content of the BaO component to 10.0% or less. Accordingly, the content of the BaO component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The BaO component can be contained in the glass using, for example, BaCO ₃ , Ba (NO ₃ ) ₂ , BaF ₂ or the like as a raw material.

  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 10.0% or less. Thereby, a desired refractive index can be easily obtained. Therefore, the mass sum (MgO + CaO + SrO + BaO) of the oxide conversion composition with respect to the total glass mass is preferably 10.0%, more preferably less than 8.0%, and most preferably less than 5.0%.

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

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

The Al ₂ O ₃ component is a component that improves the chemical durability of the glass and improves the devitrification resistance of the molten glass, and is an optional component in the optical glass of the present invention. In particular, by setting the content of the Al ₂ O ₃ component to 10.0% or less, it is possible to weaken the devitrification tendency of the glass and improve the stability of the glass. Therefore, the content of the Al ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. The 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 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 glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 7.0%. Although there is no technical disadvantage even if it does not contain the ZrO ₂ component, it is preferably 0.5%, more preferably 1.0%, most preferably in order to easily obtain the effect of enhancing devitrification resistance. Preferably, the lower limit is 2.0%. The ZrO ₂ component can be contained in the glass using, for example, ZrO ₂ , ZrF ₄ or the like as a raw material.

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. Accordingly, the content of the TiO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, and most preferably 5.0%. TiO ₂ component may be contained in the glass by using as the starting material for example TiO ₂ or the like.

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 20.0% 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 glass mass of the oxide conversion composition is preferably 20.0% as an upper limit, more preferably less than 10.0%, and most preferably less than 5.0%. To do. 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. Therefore, the content of the TeO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably 20.0% as an upper limit, 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 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 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 0.7%, and most preferably 0.5%. The Sb ₂ O ₃ component can be contained in the glass using, for example, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ · 5H ₂ O, or the like as a raw material.

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

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 glass mass of 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 cannot be expressed directly in the description of mol% because the composition is expressed by mass% with respect to the total mass of the glass of oxide conversion composition, but various properties required in the present invention. The composition expressed by mol% of each component present in the glass composition satisfying the above conditions generally takes the following values in terms of oxide conversion.
B ₂ O ₃ component 7.0~50.0mol%,
La ₂ O ₃ component 4.0~25.0mol%, and WO ₃ components 0.5~15.0mol%,
And
Li ₂ O component 0～20.0Mol% and / or _Gd 2 _{O 3} component 0～10.0Mol% and / or _Y 2 _{O 3} component 0～7.0Mol% and / or _Yb 2 _{O 3} component 0-5. 0 mol% and / or _Lu 2 _{O 3} component 0～4.0Mol% and / or _Ta 2 _{O 5} component 0～10.0Mol% and / or ZnO component 0～60.0Mol% and / or Na ₂ O component 0 15.0 mol% and / or _{K 2} O ingredient 0～10.0Mol% and / or SiO ₂ component 0～30.0Mol% and / or _Nb 2 _{O 5} component 0～5.0Mol% and / or MgO component 0 30.0 mol% and / or CaO component 0～20.0Mol% and / or SrO component 0～15.0Mol% and / or BaO component 0～10.0Mol% and / or _P 2 _{O 5} component 0 0.0Mol% and / or GeO ₂ component 0～7.0Mol% and / or _Al 2 _{O 3} component 0～12.0Mol% and / or ZrO ₂ component 0～10.0Mol% and / or TiO ₂ component 0 15.0 mol% and / or _Bi 2 _{O 3} component 0～7.0Mol% and / or TeO ₂ component 0～15.0Mol% and / or _Sb 2 _{O 3} component 0～0.3Mol%
And the total amount as F of the fluoride substituted with one or two or more oxides of each of the above metal elements as 0 to 40.0 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible, and 1100 to 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 33, most preferably 35 as a lower limit, preferably 50, more preferably 47, and most preferably 45. . As a result, the degree of freedom in optical design is increased, and a large amount of light refraction can be obtained even if the device is made thinner.

Moreover, the optical glass of the present invention has a 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 ×) in the range of ν _d > 25 with respect to the Abbe number (ν _d ). The relationship of ν _d +0.6571) ≦ (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. Here, the partial dispersion ratio (θg, F) of the optical glass at ν _d > 25 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 set as the lower limit. On the other hand, the upper limit of the partial dispersion ratio (θg, F) of the optical glass is preferably (−2.50 × 10 ⁻³ × ν _d +0.6971), more preferably (−2.50 × 10 ⁻³ ×). (ν _d +0.6921), and most preferably (−2.50 × 10 ⁻³ × ν _d +0.6871).

  Moreover, the optical glass of the present invention needs to have high devitrification resistance. In particular, the optical glass of the present invention preferably has a low liquidus temperature of 1250 ° C. or lower. More specifically, the upper limit of the liquidus temperature of the optical glass of the present invention is preferably 1250 ° C, more preferably 1200 ° C, and most preferably 1100 ° 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. Further, since the viscosity range in which the preform material can be stably produced is widened, the preform material can be formed even if the melting temperature of the glass is lowered, and the energy consumed when the preform material is formed 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 reasonably high viscosity at the liquidus temperature. In particular, the value of the logarithmic log η of the viscosity η [dPa · s] at the liquidus temperature of the optical glass of the present invention is preferably 0.90, more preferably 1.00, and most preferably greater than 1.10. Value. The log η value is preferably 2.00, more preferably 1.80, and most preferably 1.60. Thereby, since the striae of the glass to be formed is reduced, a glass suitably used as an optical element can be produced. In addition, since the surface tension of the molten glass can be increased while maintaining the deformability of the molten glass, a preform material having a larger diameter can be produced with a good shape by means such as flotation molding.

  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 660 ° C., and most preferably 640 ° 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.

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 360 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.

[Preform materials and optical elements]
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.

Composition of Examples (No. 1 to No. 120) and Comparative Examples (No. A to E) of the present invention, and the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio of these glasses (Θg, F), glass transition point (Tg), yield point (At), and wavelength (λ ₅ , λ ₇₀ and λ ₈₀ ) with spectral transmittances of 5%, 70% and 80% are shown. 1 to Table 13 below. Moreover, the result of the viscosity ((eta)) in the liquid phase temperature and liquid phase temperature of the Example (No.1-No.120) of this invention and a comparative example (No.AE) is shown in Tables 14-19. . The following examples are merely for illustrative purposes, and are not limited to these examples.

  As for the optical glass of the Example (No.1-No.120) of this invention, and the glass of a comparative example (No.A-E), all are the oxide, hydroxide, and carbonate which are respectively corresponded as a raw material of each component. , Nitrates, fluorides, hydroxides, metaphosphoric acid compounds, and other high-purity raw materials used in ordinary optical glass are selected and weighed so as to have the composition ratios of the respective examples shown in Tables 1 to 13. And then uniformly mixed, then 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 homogenized with stirring, etc. The glass was produced by casting and slowly cooling.

Here, the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio of the optical glass of the example (No. 1 to No. 120) and the glass of the comparative example (No. A to E) ( θg, F) was measured based on Japan Optical Glass Industry 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 liquid phase temperature of the glass of an Example (No.1-No.120) and a comparative example (No.A-E) is as follows. Put it in a completely melted state at 1250 ° C., drop it to any temperature set in steps of 20 ° C. from 1180 ° C. to 1000 ° C. and hold it for 12 hours. The lowest temperature at which no crystals were observed was determined by observing the presence or absence of crystals.

  Moreover, the viscosity (eta) (dPa * s) in the liquidus temperature of the optical glass of an Example (No.1-No.120) and the glass of a comparative example (No.AE) uses a ball pulling-up-type viscometer, The viscosity at the liquidus temperature was measured. In addition, when expressing a viscosity in Table 14-Table 19, it represented with the common logarithm log (eta) of viscosity (eta).

  Moreover, the horizontal type | mold expansion measuring device was used for the glass transition point (Tg) and yield point (At) of the optical glass of an Example (No.1-No.120) and the glass of a comparative example (No.AE). It was determined by measuring. 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, about the transmittance | permeability of the optical glass of an Example (No.1-No.120) and the glass of a comparative example (No.AE), 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. 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.

  As shown in Tables 14 to 19, all of the optical glasses of Examples (No. 1 to No. 120) of the present invention have a liquidus temperature of 1250 ° C. or lower, more specifically 1160 ° C. or lower. Was within the desired range. 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 viscosity at a liquidus temperature of 0.90 or more, more specifically 1.00 or more, and were within a desired range. For this reason, it became clear that the optical glass of the Example of this invention has high viscosity in liquidus temperature.

  In addition, as shown in Tables 1 to 13, all of the optical glasses of the examples of the present invention have a glass transition point (Tg) of 680 ° C. or lower, more specifically 639 ° C. or lower, and a desired range. It was in. For this reason, it became clear that the optical glass of the Example of this invention has a low glass transition point (Tg). Further, the optical glasses of the examples of the present invention all had a yield point (At) of 720 ° C. or less, more specifically 678 ° C. or less, and were within a desired range.

In addition, in the optical glasses of the examples of the present invention, λ ₇₀ (wavelength at 70% transmittance) was 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 at 5% transmittance) was 400 nm or less, more specifically, 356 nm or less. The optical glasses of the examples of the present invention all had λ ₈₀ (wavelength at 80% transmittance) of 500 nm or less, more specifically 468 nm or less. For this reason, it became clear that the optical glass of the Example of this invention was hard to color.

The optical glasses of the examples of the present invention all have a refractive index (n _d ) of 1.75 or more, more specifically 1.82 or more, and the refractive index (n _d ) of 1.95 or less. More specifically, it was 1.89 or less, which was within a desired range.

The optical glasses of the examples of the present invention each have an Abbe number (ν _d ) of 30 or more, more specifically 36 or more, and this Abbe number (ν _d ) of 50 or less, more specifically 42. 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 +0.6689) or more. On the other hand, the partial dispersion ratio (-2.50 × 10 ⁻³ × ν _d +0.6971) or less of the optical glass of the embodiment of the present invention, more specifically (−2.50 × 10 ⁻³ × ν _d). +0.6721) or less. Therefore, it was found that these partial dispersion ratios (θg, F) are within a desired range.

Therefore, the optical glass of the embodiment of the present invention has both a low refractive index (n _d ) and an Abbe number (ν _d ) within a desired range, and has a small striae and hardly devitrification, and has a diameter. It was revealed that a large preform material can be formed, press molding by heat softening is easy, coloration is small, and chromatic aberration is small.

  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 (23)

The entire mass of the glass in terms of oxide composition, 5.0 to 35.0% of _B 2 _{O 3} component in wt.%, _La 2 _{O 3} component from 15.0 to 50.0%, and WO ₃ components An optical glass containing 1.0 to 25.0% and a Li ₂ O component content of 5.0% or less. The entire mass of the glass in terms of oxide composition, 0~30.0% _Gd 2 _{O 3} component in% by weight and / or _Y 2 _{O 3} component from 0 to 15.0% and / or _Yb 2 _{O 3} component 0 15.0% and / or Lu ₂ O ₃ component 0-10.0%
The optical glass according to claim 1, further comprising: The mass sum of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, Lu) with respect to the total glass mass of the oxide equivalent composition is 20.0% or more and 60 The optical glass according to claim 1, which is 0.0% or less. 4. The optical glass according to claim 2, wherein a mass ratio La ₂ O ₃ / (Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ ) of the oxide equivalent composition is 1.50 or more and 15.00 or less. . The optical glass according to any one of claims 1 to 4, further comprising 25.0% or less of Ta ₂ O ₅ component by mass% with respect to the total mass of the glass having an oxide equivalent composition. The optical glass according to claim 5, wherein the content of Ta ₂ O ₅ component is 1.0% or more by mass% with respect to the total mass of the glass having an oxide equivalent composition.   The optical glass according to any one of claims 1 to 6, wherein the content of the ZnO component is 40.0% or less by mass% with respect to the total mass of the glass having an oxide equivalent composition.   The optical glass according to claim 7, wherein the content of the ZnO component is less than 14.0% by mass with respect to the total mass of the glass having an oxide equivalent composition.   The optical glass according to claim 7, wherein the ZnO component content is 14.0% or more in terms of% by mass relative to the total mass of the glass having an oxide equivalent composition. Na ₂ O component 0 to 10.0% and / or K ₂ O component 0 to 10.0% by mass% with respect to the total glass mass of the oxide equivalent composition
The optical glass according to claim 1, further comprising: The mass 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 glass mass of the oxide equivalent composition is 10.0% or less. The optical glass according to any one of 10. The entire mass of the glass in terms of oxide composition, from claim 1, further comprising the components of the SiO ₂ component from 0 to 15.0% and / or _Nb less than 2 _{O 5} component from 0 to 10.0% by mass% 11. Optical glass in any one of 11. The mass ratio (Rn ₂ O + La ₂ O ₃ + Gd ₂ O ₃ ) / (SiO ₂ + B ₂ O ₃ + Ta ₂ O ₅ + WO ₃ + Nb ₂ O ₅ ) of the oxide equivalent composition is 0.59 or more and 3.00 or less Item 13. An optical glass according to Item 12. MgO component 0 to 10.0% and / or CaO component 0 to 10.0% and / or SrO component 0 to 10.0% and / or BaO component in mass% with respect to the total glass mass of oxide conversion composition 0 to 10.0%
The optical glass according to claim 1, further comprising:   The sum of masses 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 glass mass of the oxide equivalent composition is 10.0% or less. Optical glass. P ₂ O ₅ component 0 to 10.0% and / or GeO ₂ component 0 to 10.0% and / or Al ₂ O ₃ component 0 to 10% by mass with respect to the total glass mass of the oxide equivalent composition. 0% and / or ZrO ₂ component 0-10.0% and / or TiO ₂ component 0-10.0% and / or Bi ₂ O ₃ component 0-20.0% and / or TeO ₂ component 0-20. 0% and / or Sb ₂ O ₃ component 0-1.0%
Each component of
The optical content according to any one of claims 1 to 15, wherein a content of F as a substitution of a part or all of one or more oxides of each metal element is 0 to 6.0%. Glass. The optical glass according to claim 1, 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.   The optical glass according to claim 1, which has a glass transition point (Tg) of 680 ° C. or lower.   The optical glass according to claim 1, which has a liquidus temperature of 1250 ° C. or lower.   A preform material comprising the optical glass according to claim 1.   An optical element produced by press-molding the preform material according to claim 20.   An optical element using the optical glass according to claim 1 as a base material.   An optical apparatus comprising the optical element according to claim 21.