JP2012166961A - Optical glass, preform material, and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass in which the use of a costly material is reduced and the devitrification resistance is high though a refractive index (n) and Abbe number (ν) are within a desired range, and to provide a preform material and an optical element that use the same.SOLUTION: The optical glass includes: by mass%, 5.0-30.0% of a BOcomponent; 15.0-50.0% of an LaOcomponent; and at most 10.0% of a NbOcomponent based on the glass total mass of an oxide conversion composition. In addition, the preform material and the optical element comprise the optical glass.

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 and 2 are known.

JP 2008-001551 A JP-A-2005-247613

  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, 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.

  In addition, in order to reduce the material cost of the optical glass, it is desirable that the raw material costs of the components constituting the optical glass be as low as possible. However, it is difficult to say that the glass compositions described in Patent Documents 1 and 2 sufficiently satisfy these various requirements.

The present invention has been made in view of the above problems, and an object thereof is to provide an expensive material while the refractive index (n _d ) and the Abbe number (ν _d ) are within a desired range. It is an object of the present invention to provide a preform material that is reduced in use and has high devitrification resistance.

In order to solve the above-mentioned problems, the present inventors have conducted intensive test studies, and as a result, the content of the Nb ₂ O ₅ component is reduced with respect to the glass containing the B ₂ O ₃ component and the La ₂ O ₃ component. As a result, it was found that the material cost of the glass was reduced while having the desired refractive index and Abbe number, and the liquidus temperature of the glass was lowered, and the present invention was completed. Specifically, the present invention provides the following.

(1) It contains 5.0 to 30.0% of the B ₂ O ₃ component and 15.0 to 50.0% of the La ₂ O ₃ component in mass% with respect to the total glass mass of the oxide equivalent composition. optical glass content of _Nb 2 _{O 5} component is 10.0%.

(2) Gd ₂ O ₃ component 0 to 35.0% 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 optical glass according to (1) or (2), which contains more than 1.0% of a Gd ₂ O ₃ component in mass% with respect to the total mass of the glass having an oxide equivalent composition.

(4) Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, Lu, Sc) with respect to the total glass mass of the oxide equivalent composition is 20 Optical glass in any one of (1) to (3) which is 0.0% or more and 65.0% or less.

(5) any description of the optical glass of the mass ratio _{La 2 O 3 / Ln 2 O} 3 oxide composition in terms of is 0.85 or less (1) (4).

(6) SiO ₂ component 0 to 15.0% and / or WO ₃ component 0 to 25.0% in mass% with respect to the total glass mass of the oxide equivalent composition
The optical glass according to any one of (1) to (5), further comprising:

(7) The optical glass according to (6), wherein the content of the WO ₃ component is greater than 3.0% in terms of mass% with respect to the total mass of the glass having an oxide equivalent composition.

(8) The optical glass according to any one of (1) to (7), wherein a mass sum of (SiO ₂ + B ₂ O ₃ + WO ₃ ) having an oxide equivalent composition is 15.0% or more and 50.0% or less.

(9) The optical glass according to (8), wherein the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + WO ₃ ) of the oxide equivalent composition is 2.25 or less.

(10) the entire mass of the glass in terms of oxide composition, 0 to 40.0% ZnO component in% by weight and / or Li ₂ O component from 0 to 5.0%
The optical glass according to any one of (1) to (9), further containing each component of

(11) The optical glass according to (10), wherein the mass ratio WO ₃ / (ZnO + Li ₂ O + WO ₃ ) of the oxide equivalent composition is 0.3 or more.

(12) TiO ₂ component 0 to 10.0% and / or Ta ₂ O ₅ component 0 to 20.0% by mass% with respect to the total glass mass of the oxide equivalent composition
The optical glass according to any one of (1) to (11), further comprising:

(13) 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 (12), further comprising:

  (14) 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 15.0% or less ( 13) Optical glass as described.

(15) The Na ₂ O component 0 to 10.0% and / or the 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 any one of (1) to (14), further comprising:

(16) 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 15.0% or less ( 15) The optical glass as described.

(17) GeO ₂ component 0 to 10.0% and / or P ₂ O ₅ component 0 to 10.0% and / or ZrO ₂ component 0 to 15% by mass with respect to the total glass mass of the oxide equivalent composition 0.0% and / or Bi ₂ O ₃ component 0-20.0% and / or TeO ₂ component 0-20.0% and / or Al ₂ O ₃ component 0-10.0% and / or Ga ₂ O ₃ Component 0 to 10.0% and / or Sb ₂ O ₃ component 0 to 1.0%
Each component of
Any one of (1) to (16), 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.

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

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

  (20) The optical glass according to any one of (1) to (19), which has a liquidus temperature of 1260 ° C. or lower.

  (21) A preform material comprising the optical glass according to any one of (1) to (20).

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

  (23) An optical element having the optical glass according to any one of (1) to (20) as a base material.

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

According to the present invention, while reducing the content of the Nb ₂ O ₅ component to the glass containing the B ₂ O ₃ component and the La ₂ O ₃ component, while having the desired refractive index and Abbe number. The devitrification resistance is increased and the material cost of the glass is reduced. For this reason, a preform material having high devitrification resistance can be obtained at a lower cost while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges.

In the optical glass of the present invention, the B ₂ O ₃ component is 5.0 to 30.0% and the La ₂ O ₃ component is 15.0 to 50.0 by mass% with respect to the total glass mass of the oxide equivalent composition. %, And the content of the Nb ₂ O ₅ component is 10.0% or less. By reducing the content of the Nb ₂ O ₅ component, the amount of expensive Nb ₂ O ₅ component used is reduced, so that the raw material cost of the optical glass is reduced and the devitrification resistance is increased. 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, optical glass having high devitrification resistance and a preform material and an optical element using the same can be obtained at a lower cost while the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges. Obtainable.

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

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, unless there is particular notice, content of each component shall be displayed by the mass% with respect to the glass total mass of an oxide conversion composition. Here, the “oxide equivalent composition” means that the oxide, composite salt, metal fluoride, etc. used as 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 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 setting the content of the B ₂ O ₃ component to 5.0% or more, the devitrification resistance of the glass can be improved and the dispersion of the glass can be reduced. Therefore, the content of the B ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%, more preferably 8.0%, and most preferably 10.0%. On the other hand, by setting the content of the B ₂ O ₃ component to 30.0% or less, it is possible to easily obtain a larger refractive index and suppress deterioration of chemical durability. Moreover, this can suppress devitrification of the glass due to excessive inclusion of the B ₂ O ₃ component. Therefore, the content of the B ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 30.0%, more preferably 25.0%, still more preferably 20.0%, and most preferably 18.0. % Is the upper limit. 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. Therefore, the content of the La ₂ O ₃ component with respect to the total glass mass of the oxide equivalent composition is preferably 15.0%, more preferably 17.0%, and most preferably 18.0%. On the other hand, by setting the content of the La ₂ O ₃ component to 50.0% or less, it is possible to increase the stability of the glass and reduce the devitrification of the glass. Moreover, optical glass with a lower glass transition point can be easily obtained by reducing the content of the La ₂ O ₃ component. Therefore, the content of the La ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 50.0%, more preferably 45.0%, still more preferably 40.0%, and most preferably 37.0. % Is the upper limit. 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.

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 reducing the content of the expensive Nb ₂ O ₅ component, an optical glass having a desired optical constant and devitrification resistance can be produced at a lower material cost. Moreover, by reducing the content of Nb ₂ O ₅ component, it suppresses the deterioration of devitrification resistance of the glass due to excessive content of Nb ₂ O ₅ component, and to suppress the decrease of the transmittance of the glass to visible light be able to. Therefore, the content of the Nb ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and even more preferably 3.0%. In particular, from the viewpoint of obtaining a glass with low material cost and high devitrification resistance, the content of the Nb ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition may be less than 1.0%. The Nb ₂ O ₅ component can be contained in the glass using, for example, Nb ₂ O ₅ as a raw material.

The 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 35.0% 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 content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 35.0%, more preferably 30.0%, further preferably 25.0%, and most preferably 20.0%. % Is the upper limit. 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.

Although there is no technical disadvantage even if the Gd ₂ O ₃ component is not contained, since the number of rare earth elements contained in the glass increases by containing more than 0%, the liquidus temperature of the glass is lowered. By doing so, devitrification resistance can be further improved. Therefore, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably more than 0%, more preferably more than 1.0%, and still more preferably 2.0% as the lower limit. To do. In particular, from the viewpoint of easily obtaining a desired optical constant by increasing the refractive index and Abbe number of the glass, the content of the Gd ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 5.0%. The lower limit is more preferably 8.0%, and most preferably 10.0%.

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 and / or the Yb ₂ O ₃ component 15.0% or less, or by making the content of the Lu ₂ O ₃ component 10.0% or less, glass The desired optical constant can be easily obtained, and the devitrification resistance of the glass can be improved. Therefore, the content of Y ₂ O ₃ and Yb ₂ O ₃ with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 5.0%, respectively. And Further, the content of each component of Lu ₂ O ₃ with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0%. . 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.

Although none of these components is technically disadvantageous, Lu ₂ O ₃ is used in combination with other Ln ₂ O ₃ components described below, so that the liquidus temperature of the glass Can be further reduced. Therefore, the content of the Lu ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 0.001%, more preferably 0.005%, and most preferably 0.010%.

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, Lu, Sc) is 20.0% or more and 65 It is preferably 0.0% or less. In particular, by making the mass sum of the Ln ₂ O ₃ component 20.0% 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. In addition, this reduces the liquidus temperature of the glass, increases the resistance to devitrification, and increases the transmittance for light on the short wavelength side in the visible range, thereby obtaining an optical glass that is preferably used for visible light. it can. 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%, and most preferably 40.0%. On the other hand, by the mass sum of Ln ₂ O ₃ component below 65.0%, because the liquidus temperature of the glass is lowered, thereby reducing the devitrification of the glass. 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 65.0%, more preferably 60.0%, still more preferably 55.0%, and most preferably 51.0%. % Is the upper limit.

In the optical glass of the present invention, the ratio of the content of the La ₂ O ₃ component to the content of the above-described Ln ₂ O ₃ component is preferably 0.85 or less. By making this ratio within a predetermined range, the liquid phase temperature of the glass is further lowered by including a plurality of elements belonging to the above-mentioned Ln, and therefore stable even if the Ta ₂ O ₅ component is reduced. Glass can be obtained. Therefore, it is possible to obtain an optical glass that achieves both low material cost and resistance to devitrification. Therefore, the mass ratio La ₂ O ₃ / Ln ₂ O ₃ in the oxide-converted composition is preferably 0.85, more preferably 0.80, still more preferably 0.78, and most preferably 0.76. . On the other hand, the mass ratio La ₂ O ₃ / Ln ₂ O ₃ in the oxide equivalent composition is preferably 0.25, more preferably 0.30, and most preferably 0.35.

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 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 glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 8.0%. SiO ₂ component may be contained in the glass by using as a raw material such as _{SiO 2, K 2 SiF 6,} Na 2 SiF 6 or the like.

The WO ₃ component is a component that increases 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 25.0% 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 content of the WO ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 25.0%, more preferably 22.0%, and most preferably 20.0%. The optical glass of the present invention is not technical disadvantages not even include WO ₃ components, by containing a WO ₃ components, of the present invention the content of Nb ₂ O ₅ component is reduced Even if it is optical glass, since the liquidus temperature of glass becomes easy to fall more, the devitrification resistance of glass can further be improved. Moreover, the glass transition point of the optical glass obtained can be made lower. Therefore, the content of the WO ₃ component with respect to the total glass mass of the oxide conversion composition is preferably more than 0%, more preferably more than 3.0%, still more preferably 5.0%, and most preferably 10%. 0.0% is the lower limit. The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

In the optical glass of the present invention, the sum of the contents of the SiO ₂ component, the B ₂ O ₃ component and the WO ₃ component is preferably 15.0% or more and 50.0% or less. Since the liquidus temperature of the optical glass is lowered by making the sum of the contents within the range of 15.0% or more and within the range of 50.0% or less, the glass having higher devitrification resistance. Can be obtained. Therefore, the mass sum (SiO ₂ + B ₂ O ₃ + WO ₃ ) with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 20.0%, and most preferably 25.0%. To do. Moreover, the mass sum (SiO ₂ + B ₂ O ₃ + WO ₃ ) with respect to the total glass mass of the oxide conversion composition is preferably 50.0%, more preferably 45.0%, and most preferably 40.0%. To do.

In the optical glass of the present invention, the ratio of the sum of the contents of the Ln ₂ O ₃ component to the sum of the contents of the SiO ₂ component, the B ₂ O ₃ component and the WO ₃ component is 2.25 or less. preferable. As a result, the content of the Ln ₂ O ₃ component for increasing the liquidus temperature is decreased while the content of the SiO ₂ component, B ₂ O ₃ component and the WO ₃ component for decreasing the liquidus temperature is increased. The liquidus temperature can be lowered further. Therefore, the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + WO ₃ ) of the oxide equivalent composition is preferably 2.25, more preferably 2.00, and most preferably 1.70. The lower limit of the mass ratio _{Ln 2 O 3 / (SiO 2} + B 2 O 3 + WO 3) is appropriately determined depending on the range of the content of each component, generally 0.30 or more, more specifically, It is often 0.70 or more, more specifically 1.00 or more.

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 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 20.0%, still more preferably 10.0%, and most preferably 7.0%. And Although it is possible to obtain a glass having desired characteristics even if it does not contain a ZnO component, the glass transition point is lowered by containing a ZnO component, so that an optical glass that is easy to press-mold is obtained. Easy to do. Therefore, the content of the ZnO component with respect to the total glass mass of the oxide conversion composition is preferably more than 0%, more preferably 1.0%, further preferably 2.0%, and most preferably 3.0%. And The ZnO component can be contained in the glass using, for example, ZnO, ZnF ₂ or the like as a raw material.

Li 2 _O component is a component that lowers the glass transition point, which is an optional component of the optical glass of the present invention. In particular, devitrification of the glass can be reduced by setting the content of the Li ₂ O component to 5.0% or less. 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%. Although Li 2 _O component is possible to obtain a glass having the desired properties may not contain, by containing Li 2 _O component, the glass transition point tends lowered, the press-molding An easy-to-use optical glass can be obtained more easily. Therefore, the content of the Li ₂ O component with respect to the total glass mass of the oxide equivalent composition is preferably more than 0%, more preferably 0.1%, and most preferably 0.15%.

In the optical glass of the present invention, the ratio of the content of the WO ₃ component to the sum of the contents of the ZnO component, the Li ₂ O component and the WO ₃ component is preferably 0.3 or more. This increases the content of the WO ₃ component, which has a strong action of lowering the liquidus temperature among the components that lower the glass transition point, thereby increasing the devitrification resistance of the glass while obtaining the desired low glass transition point. be able to. In addition, unlike the ZnO component and the Li ₂ O component, the WO ₃ component is a component that can increase the refractive index, so that the refractive index of the glass can also be increased. Therefore, the mass ratio WO ₃ / (ZnO + Li ₂ O + WO ₃ ) of the oxide equivalent composition is preferably 0.3, more preferably 0.5, and most preferably 0.6. In addition, the upper limit of this mass ratio WO ₃ / (ZnO + Li ₂ O + WO ₃ ) is not particularly limited, and may be 1.00 (that is, not containing a ZnO component and a Li ₂ O component).

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 glass mass of the oxide conversion composition is preferably 10.0%, more preferably 8.0%, still more preferably 5.0%, and most preferably 3.0%. The upper limit. TiO ₂ component may be contained in the glass by using as the starting material for example TiO ₂ or the like.

The Ta ₂ O ₅ component is a component that increases devitrification resistance by increasing the refractive index of the glass and lowering the liquidus temperature of the glass, and is an optional component in the optical glass of the present invention. The optical glass of the present invention can produce optical glass having a desired optical constant at a lower material cost by reducing the content of expensive Ta ₂ O ₅ component. Further, by reducing the content of the Ta ₂ O ₅ component, it becomes possible to lower the temperature at which the raw material is melted, and the energy required for melting the raw material is reduced, so that the manufacturing cost of the optical glass can also be reduced. . Therefore, the content of the Ta ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 20.0%, more preferably 15.0%, and most preferably 13.0%. The optical glass of the present invention is not technical disadvantages also contain no Ta ₂ O ₅ component, by containing Ta ₂ O ₅ component, for the liquidus temperature of the glass can be further reduced Further, the devitrification resistance of the glass can be further improved. Therefore, from the viewpoint of obtaining a glass with particularly high devitrification resistance, the content of the Ta ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably more than 0%, more preferably 0.1%, More preferably, 1.0% may be the lower limit. The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

In the optical glass of the present invention, the sum of the contents of SiO ₂ component, B ₂ O ₃ component, Nb ₂ O ₅ component and Ta ₂ O ₅ component is preferably 40.0% or less. Thereby, since it becomes difficult for the glass transition point of optical glass to raise, the optical glass which can perform press molding easily can be obtained by being able to obtain easily the glass which has a low glass transition point. Therefore, the mass sum (SiO ₂ + B ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) with respect to the total mass of the glass in terms of oxide is preferably 40.0%, more preferably 35.0%, and most preferably 32. 0.0% is the upper limit.

In the optical glass of the present invention, the ratio of the content of the WO ₃ component to the sum of the content of the SiO ₂ component, the B ₂ O ₃ component, the Nb ₂ O ₅ component, and the Ta ₂ O ₅ component is 0.10 or more. It is preferable that Thereby, since the glass transition point of optical glass becomes low, the optical glass which can perform press molding easily can be obtained. Therefore, the mass ratio WO ₃ / (SiO ₂ + B ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) of the oxide conversion composition is preferably 0.10, more preferably 0.20, and most preferably 0.25. The lower limit. The upper limit of the mass ratio WO ₃ / (SiO ₂ + B ₂ O ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) is not particularly limited, but the mass ratio is 3.00 or less, more specifically 2.00 or less. More specifically, it is often 1.50 or less.

In the optical glass of the present invention, the ratio of the mass sum (TiO ₂ + WO ₃ ) to the mass sum (TiO ₂ + WO ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) is preferably 0.40 or more. Thereby, while reducing the material cost of the glass, the refractive index and dispersion of the glass are increased and the devitrification resistance is increased. Therefore, even if a rare earth such as Gd is added, an optical glass having a desired optical constant. Can be manufactured at a lower cost. Therefore, the mass ratio (TiO ₂ + WO ₃ ) / (TiO ₂ + WO ₃ + Nb ₂ O ₅ + Ta ₂ O ₅ ) of the oxide equivalent composition is preferably 0.40, more preferably 0.45, and most preferably 0.00. 50 is the lower limit. On the other hand, the upper limit of the mass ratio is not particularly limited, and may be 1.00 (that is, Nb ₂ O ₅ component and Ta ₂ O ₅ are not contained).

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 mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0. % Is the upper limit. MgO component, CaO component, SrO component, and BaO component are raw materials such as MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) ₂ , BaF _2. Etc. can be contained in the glass.

  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, it is possible to easily obtain a desired refractive index, and it is possible to reduce the occurrence of devitrification of the glass due to excessive inclusion of these components. Therefore, the upper limit of the mass sum of the RO component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, and most preferably 5.0%.

The 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, and are optional components in the optical glass of the present invention. . In particular, by making each content of the Na ₂ O component and the K ₂ O component 10.0% or less, it is difficult to lower the refractive index of the glass, and the stability of the glass is increased to cause devitrification and the like. Can be reduced. Therefore, the content of each of the Na ₂ O component and the K ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0%. The upper limit. The Na ₂ O component and the K ₂ O component use, for example, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ , K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ as raw materials. It can be contained in 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 15.0% 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 mass sum of the Rn ₂ O component with respect to the total glass mass of the oxide conversion composition is preferably 15.0%, more preferably 10.0%, still more preferably 5.0%, and most preferably 3.0%. Is the upper limit.

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 mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0%. The GeO ₂ component can be contained in the glass using, for example, GeO ₂ as a raw material.

P ₂ O ₅ component is a component having an effect of improving resistance to devitrification and lower the liquidus temperature of the glass, an optional component of the optical glass of the present invention. In particular, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress a decrease in chemical durability, particularly water resistance, of the glass. Therefore, the content of the P ₂ O ₅ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0%. 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 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 15.0%, more preferably 12.0%, still more preferably 10.0%, and most preferably 7.0%. The upper limit. On the other hand, by containing the ZrO ₂ component, it is possible to easily obtain the performance of high refractive index and low dispersion and to easily obtain the effect of increasing the devitrification resistance. Therefore, the content of the ZrO ₂ component with respect to the total glass mass of the oxide conversion composition is preferably more than 0%, more preferably 0.5%, even more preferably 1.6%, and most preferably 2.0%. Is the lower limit. 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 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 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 10.0% or less, the devitrification tendency of the glass can be weakened and the stability of the glass can be improved. Therefore, the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component with respect to the total glass mass of the oxide conversion composition is preferably 10.0%, more preferably 5.0%, and most preferably 3.0%. % Is the upper limit. The Al ₂ O ₃ component and the Ga ₂ O ₃ component should be contained in the glass using, for example, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga (OH) _3, etc. as raw materials. Can do.

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. Therefore, the content of the Sb ₂ O ₃ component with respect to the total glass mass of the oxide-converted composition is preferably 1.0%, more preferably 0.7%, 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 from 7.0 to 45.0 mol%, and _La 2 _{O 3} component from 4.0 to 25.0 mol%,
Nb ₂ O ₅ component 0-5.0 mol% and / or Gd ₂ O ₃ component 0-12.0 mol% and / or Y ₂ O ₃ component 0-7.0 mol% and / or Yb ₂ O ₃ component 0-5.0 mol% and / or _Lu 2 _{O 3} component 0-4.0 mol% and / or SiO ₂ component from 0 to 30.0 mol% and / or WO ₃ components from 0 to 15.0 mol% and / or ZnO component from 0 to 60.0 mol% and / or Li ₂ O component 0 to 20.0 mol% and / or TiO ₂ component from 0 to 15.0 mol% and / or _Ta 2 _{O 5} component 0-10. 0 mol% and / or MgO component 0 to 30.0 mol% and / or CaO component 0 to 20.0 mol% and / or SrO component 0 to 15.0 mol% and / or BaO component 0 to 10.0 0 to 15.0 mol% mol% and / or Na ₂ O component and / or ₂ O component 0 to 10.0 mol% and / or GeO ₂ component from 0 to 7.0 mol% and / or _P 2 _{O 5} component 0 to 10.0 mol% and / or _Bi 2 _{O 3} component 0-7. 0 mol% and / or ZrO ₂ component from 0 to 15.0 mol% and / or TeO ₂ component from 0 to 15.0 mol% and / or _Al 2 _{O 3} component from 0 to 12.0 mol% and / or _Ga 2 O ₃ ingredients 0-5.0 mol% and / or _Sb 2 _{O 3} component to 0.3 mole%
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 each said metal element as 0-40.0 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, 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 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 high devitrification resistance. In particular, the optical glass of the present invention preferably has a low liquidus temperature of 1260 ° C. or lower. More specifically, the liquidus temperature of the optical glass of the present invention is preferably 1260 ° C., more preferably 1200 ° C., further preferably 1160 ° C., further preferably 1100 ° C., and most preferably less than 1060 ° C. To do. 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-shaped glass sample is placed in a platinum crucible in a platinum crucible having a capacity of 50 ml and completely melted at 1300 ° 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 1280 ° C. to 1000 ° C.

  Moreover, it is preferable that the optical glass of this invention has a glass transition point (Tg) of 680 degrees C or less. 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 500 nm or less, more preferably 450 nm or less, and most preferably. Is 420 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 520 nm or less, more preferably 500 nm or less, and most preferably 480 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 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. 23) and Comparative Examples (No. A to No. B) of the present invention, and refractive indexes (n _d ), Abbe numbers (ν _d ), and parts of these glasses Dispersion ratio (θg, F), glass transition point (Tg), yield point (At), liquidus temperature, and wavelengths exhibiting spectral transmittance of 5%, 70% and 80% (λ ₅ , λ ₇₀ and λ ₈₀ ) Results are shown in Tables 1 to 4. 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.23) of this invention, and the glass of a comparative example (No.A-No.B), all are an oxide, a hydroxide, respectively corresponding as a raw material of each component, High purity raw materials used for ordinary optical glass such as carbonates, nitrates, fluorides, hydroxides, metaphosphoric acid compounds are selected, and the proportions of the compositions of the examples and comparative examples shown in Tables 1 to 4 After being weighed and uniformly mixed, it is put into a platinum crucible and 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. After that, it was cast into a mold and gradually cooled to produce a glass.

Here, the refractive index (n _d ), Abbe number (ν _d ), and partial dispersion of the optical glass of the example (No. 1 to No. 23) and the glass of the comparative example (No. A to No. B). 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 optical glass of an Example (No.1-No.23) and the glass of a comparative example (No.A-No.B) are horizontal expansion measuring instruments. It calculated | required by performing the used measurement. 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 optical glass of an Example (No.1-No.23) and the glass of a comparative example (No.A-No.B) 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 liquid phase temperature of the glass of an Example (No.1-No.23) and a comparative example (No.A-No.B) is platinum in a platinum crucible with a capacity of 50 ml. Put it in a crucible and make it completely melted at 1300 ° C, drop it to any temperature set in increments of 20 ° C from 1280 ° C to 1000 ° C and hold it for 12 hours. The presence or absence of crystals in the glass was observed, and the lowest temperature at which no crystals were observed was determined.

  As shown in Tables 1 to 3, all of the optical glasses of Examples (No. 1 to No. 23) of the present invention have a liquidus temperature of 1260 ° C. or lower, more specifically 1040 ° C. or lower. Was within the desired range. On the other hand, as shown in Table 4, the comparative example (No. A) had a liquidus temperature higher than 1040 ° C. Further, the comparative example (No. B) was devitrified. For this reason, it became clear that the optical glass of the Example of this invention has high devitrification resistance, although it can manufacture cheaply compared with the glass of a comparative example.

The optical glasses of the examples of the present invention all had λ ₇₀ (wavelength at 70% transmittance) of 500 nm or less, more specifically 404 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, 357 nm or less. The optical glasses of the examples of the present invention all had a λ ₈₀ (wavelength at 80% transmittance) of 520 nm or less, more specifically 460 nm or less. For this reason, it became clear that the optical glass of the Example of this invention was hard to color.

  In addition, as shown in Tables 1 to 3, 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 624 ° 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 671 ° C. or less, and were 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 1.86 or more, and this refractive index (n _d ) is 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 all have an Abbe number (ν _d ) of 30 or more, more specifically 36 or more, and the Abbe number (ν _d ) of 50 or less, more specifically 38. 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. 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). +0.6724) 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 a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges and has a low glass transition point. It has become clear that it has high devitrification property, is easy to press-mold by heat softening, and has little coloring.

  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 (24)

It contains 5.0 to 30.0% of the B ₂ O ₃ component and 15.0 to 50.0% of the La ₂ O ₃ component in terms of% by mass with respect to the total glass mass of the oxide conversion composition, and Nb ₂ Optical glass whose content of O ₅ component is 10.0% or less. The entire mass of the glass in terms of oxide composition, 0~35.0% _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: Oxides by mass% with respect to the glass the total weight of the composition in terms of, claim 1 or 2, wherein the optical glass contains more than 1.0% of Gd ₂ O ₃ component. 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, Sc) with respect to the total glass mass of the oxide equivalent composition is 20.0% The optical glass according to any one of claims 1 to 3, which is 65.0% or less. 5. The optical glass according to claim 1, wherein a mass ratio La ₂ O ₃ / Ln ₂ O _{3 of the} oxide equivalent composition is 0.85 or less. SiO ₂ component 0 to 15.0% and / or WO ₃ component 0 to 25.0% in terms of mass% with respect to the total mass of the glass in oxide equivalent composition
The optical glass according to claim 1, further comprising: The optical glass according to claim 6, wherein the content of the WO ₃ component is more than 3.0% in terms of% by mass relative to the total mass of the glass in terms of oxide. The optical glass according to any one of claims 1 to 7, wherein a mass sum of (SiO ₂ + B ₂ O ₃ + WO ₃ ) having an oxide equivalent composition is 15.0% or more and 50.0% or less. 9. The optical glass according to claim 8, wherein the mass ratio Ln ₂ O ₃ / (SiO ₂ + B ₂ O ₃ + WO ₃ ) of the oxide equivalent composition is 2.25 or less. ZnO component 0 to 40.0% and / or Li ₂ O component 0 to 5.0% by mass% with respect to the total glass mass of the oxide conversion composition
The optical glass according to claim 1, further comprising: 11. The optical glass according to claim 10, wherein a mass ratio WO ₃ / (ZnO + Li ₂ O + WO ₃ ) of the oxide equivalent composition is 0.3 or more. TiO ₂ component 0 to 10.0% and / or Ta ₂ O ₅ component 0 to 20.0% in mass% with respect to the total glass mass of oxide conversion composition
The optical glass according to claim 1, further comprising: 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:   14. 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 15.0% or less. Optical glass. 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 15.0% or less. Optical glass. GeO ₂ component 0 to 10.0% and / or P ₂ O ₅ component 0 to 10.0% and / or ZrO ₂ component 0 to 15.0% by mass% with respect to the total glass mass of oxide conversion composition and / or _Bi 2 _{O 3} component from 0 to 20.0% and / or TeO ₂ component from 0 to 20.0% and / or _Al 2 _{O 3} component from 0 to 10.0% and / or _Ga 2 _{O 3} component 0 10.0% and / or Sb ₂ O ₃ component 0-1.0%
Each component of
The optical content according to any one of claims 1 to 16, wherein a 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%. 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 1260 ° C. or lower.   A preform material comprising the optical glass according to any one of claims 1 to 20.   An optical element produced by press-molding the preform material according to claim 21.   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 22.