JP5669341B2 - Optical glass, optical element and precision press molding preform - Google Patents

Description

The present invention relates to a Bi ₂ O ₃ optical glass containing a high amount of Bi ₂ O ₃ , and more specifically, an optical constant having an optical constant of a refractive index (nd) of 2.1 or more and an Abbe number (νd) of 20 or less. Related to glass.

In recent years, integration and high functionality of devices including an optical system have been rapidly advanced, and demands for high accuracy, light weight, and miniaturization of the optical system are rapidly increasing. In order to meet these demands, it is necessary to use an aspheric lens that is effective in reducing the number of lenses and to use a high refractive glass material that is effective in reducing the thickness of the lens.

For manufacturing aspherical lenses, precision press molding that does not require grinding or polishing is generally used. The optical glass used in precision press molding is a low Tg optical glass that softens at a lower temperature than the optical glass used after grinding and polishing. The lower the glass transition point (Tg) of the low Tg optical glass used here, the shorter the molding time, the lower the molding energy, and the longer the life of the mold material, making it possible to manufacture lenses at low cost. .

As a glass having a high refractive index, a high dispersion region, and a low glass transition point (Tg), a glass containing a large amount of Bi2O3 has been developed. For example, Non-Patent Documents 1 and 2 disclose PbO-Bi2O3- (heavy metal) glass having a high refractive index, but use harmful substances such as PbO and Tl2O, which is a problem as optical glass. There is.

Non-patent documents 3 and 4 disclose glasses such as TeO ₂ —Bi ₂ O ₃ —WO ₃ and Bi ₂ O ₃ —Ga ₂ O ₃ — (K ₂ O, Cs ₂ O, Na ₂ O). However, both have an absorption edge in the range of 480 to 550 nm and are difficult to use as optical glass.
Further, Non-Patent Documents 1 and 2 disclose experimental results of a gold crucible and a platinum crucible as the crucible material dependency of physical properties. In the case of a platinum crucible, the platinum melts by melting and is greatly colored. In the case of a gold crucible, although it is not colored, since the melting point of gold itself is low, the upper limit temperature is limited and fining cannot be performed, and it is difficult to satisfy the quality required for optical glass. When production is considered as described above, it can be said that any Bi ₂ O ₃ high content composition still has a big problem.

Further, Patent Documents 1, 2 and 3 describe high refractive index and high dispersion glass containing a large amount of B ₂ O ₃ and Bi ₂ O ₃ . However, the glass described in these documents has a refractive index of less than 2.1, and if Bi ₂ O ₃ is added until the refractive index exceeds 2.1, the stability during melting and molding decreases. However, there are disadvantages such as a decrease in yield.
American Ceramic Society, P, 1017-24, Vol77, No4, 1994 American Ceramic Society, P.M. 2315, Vol. 75, no. 9, October 1992 American Ceramic Society Bulletin, P.A. 1543, Vol. 71, no. 10, October 1992 Glass Technology, P.M. 106, Vol. 28, no. 2, April 1987 JP 2006-327926 A JP 2007-106625 A JP 2002-201039 A

The object of the present invention is to comprehensively solve the above disadvantages of the prior art, having an optical constant having a refractive index (nd) of 2.1 or more and an Abbe number (νd) of 20 or less , and a glass transition point ( The object is to provide an optical glass having a sufficiently low Tg) and high productivity.

As a result of intensive studies to solve the above-mentioned problems, the present inventor contains 82% or more of Bi ₂ O ₃ and contains at least one of B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ as other formers. In the glass, the RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, Mg) is contained in a predetermined amount, and the RO component and the Rn2O component (Rn is Li, Na, K, Cs, By limiting the balance between the RO component and the Bi ₂ O ₃ content to a predetermined range, the refractive index (nd) exceeds 2.1, and the glass transition point is at least one selected from the group consisting of Rb) It was found that (Tg) is sufficiently low and a desired optical glass capable of stable production can be obtained, and the present invention has been developed. More specifically, the following is provided.

(1) It contains 82% or more of Bi ₂ O ₃ in mass% based on oxide,
An optical glass having a refractive index (nd) of 2.1 or more and an Abbe number (νd) of 20 or less.

(2) The optical glass as described in (1), wherein the glass transition point (Tg) is 500 ° C. or lower.

(3) RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, Mg) and / or Rn ₂ O component (Rn is Li, Na, K) in mass% based on oxide. The optical glass according to any one of (1) and (2), containing 0.1% or more of one or more selected from the group consisting of Cs, Rb.

(4) Oxygen-based mass%, RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, Mg) exceeds 0% and any of (1) to (3) Optical glass according to crab.

(5) Any one of (1) to (3), containing 0.1% to 10% of one or both of a TeO ₂ component and a SeO ₂ component in mass% based on an oxide The optical glass described in 1.

(6) The optical glass according to any one of (1) to (5), wherein the total content of B ₂ O ₃ , SiO _2, and Al ₂ O ₃ is 0.1% or more by mass% based on oxide. .

(7)% by mass based on oxide,
ZnO 0-15%, and / or BaO 0-15%, and / or SrO 0-15%, and / or CaO 0-15%, and / or MgO 0-15%,
However, the total content of RO (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, Mg) is more than 0% and 15% or less, and / or Li ₂ O 0-15%, and / or Or Na ₂ O 0-15%, and / or K ₂ O 0-15%, and / or Cs ₂ O 0-15%,
However, the total content of Rn ₂ O (Rn is one or more selected from the group consisting of Li, Na, K, Cs) is 0 to 15% or less, and / or B ₂ O _{3 0 to} 15%, and / or SiO ₂ 0-15% and / or Al ₂ O ₃ 0-15% and / or TiO ₂ 0-15% and / or Nb ₂ O ₅ 0-15% and / or WO ₃ 0-15% And / or Ta ₂ O ₅ 0-15% and / or ZrO ₂ 0-15% and / or Y ₂ O ₃ 0-15% and / or La ₂ O ₃ 0-15% and / or Gd ₂ O ₃ 0-15% and / or Yb ₂ O ₃ 0-15% and / or P ₂ O ₅ 0-15% and / or Sb ₂ O ₃ 0-15% and / or Ge ₂ O ₃ 0~15%, F for some or all of the oxide containing the respective components were fluoride substitution (1) to (6), wherein the total amount is 10% or less when expressed in terms of mass% when calculated as F atoms based on 100 mass% of the oxide-based composition. The optical glass according to any one of the above.

(8) The optical glass according to any one of (1) to (7), wherein the wavelength at a spectral transmittance of 5% (10 mm thickness) including reflection loss is 470 nm or less.

(9) A precision press-molding preform comprising the optical glass according to any one of (1) to (8).

(10) An optical element comprising the optical glass according to any one of (1) to (8).

(11) An optical element formed by precision pressing the preform of (9).

The optical glass of the present invention has a high refractive index and high dispersion having a low glass transition point, having a refractive index (nd) of 2.1 or more and an Abbe number (νd) of 20 or less, by adopting the above-mentioned constituent requirements. Optical glass can be obtained. Since this glass has a high refractive index, the lens thickness can be reduced and the dispersion is characteristic. Therefore, the degree of freedom in optical design is increased, and the optical device can be reduced in weight and size. Moreover, since the glass transition point is sufficiently low as described above, it can be used as an optical glass for precision press molding. The low glass transition temperature makes it possible to keep the temperature of precision press molding low. As a result, it contributes to longer mold life and improved mold release properties between glass and release film.

Furthermore, by taking a balance between suitable amount situ Bi ₂ O ₃ component RO components, it is possible to improve the glass stability. In addition, by containing an alkali metal component, a sufficiently low glass transition point (Tg) can be obtained while maintaining a stable glass state, and the melting temperature is lowered to perform melting at a relatively low temperature. I can do things.

Next, specific embodiments of the optical glass of the present invention will be described.

(Glass component)
The composition range of each component constituting the optical glass of the present invention is described below. Each component is expressed in mass%. In addition, all the glass compositions represented by the mass% in this-application specification are represented by the mass% on the basis of an oxide. Here, the “oxide standard” means that the oxide, composite salt, metal fluoride, etc. used as the raw material of the glass component of the present invention are all decomposed and converted into oxide when melted. The total amount of oxides is 100% by mass, and is a composition that describes each component contained in the glass. The total amount of F in which a part or all of the oxides are fluoride-substituted is the composition of the present invention. The fluorine content that may be present in the glass composition is expressed in terms of mass% when calculated as F atoms based on the oxide reference composition of 100%.

<About essential and optional components>
The Bi ₂ O ₃ component is an indispensable component for improving the stability of the glass, and increasing the refractive index, increasing the dispersion, decreasing the Tg, and improving the chemical durability. However, if the amount is too large, the transmittance of the glass itself may be deteriorated. If the amount is too small, it is difficult to satisfy optical constants that are high in optical design needs. Therefore, the Bi ₂ O ₃ component amount is preferably 82% or more, more preferably 84%, and most preferably 85%.

The TeO ₂ component and the SeO ₂ component are extremely effective components for improving the defoaming property while maintaining a high refractive index and a low glass transition point in the optical glass containing a large amount of the Bi ₂ O ₃ component. However, if excessively contained, the stability of the glass tends to be lowered. Moreover, by containing these components, the temperature of the refining process can be lowered and the gold crucible can be dissolved. Accordingly, the total of one or both of these components is preferably 0.1%, more preferably 0.3%, most preferably 0.5%, preferably 10%, more preferably 8%, most preferably Preferably, the upper limit is 3%. The content of each component is preferably 10%, more preferably 8%, and most preferably 3%, with no particular lower limit.

The RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, and Mg) can be contained in order to improve the melting property of the glass and adjust it to any optical constant. If excessively contained, the stability, the chemical durability, and the transmittance tend to decrease. Also, by increasing the content of Bi ₂ O ₃ has an effect of improving or maintaining the glass stability when achieving a high refractive index. The total content of RO components is preferably more than 0%, more preferably 0.5%, most preferably 1% as the lower limit, preferably 15%, more preferably 10%, most preferably 5% Is the upper limit.

In the case of a glass containing a large amount of Bi ₂ O ₃ as in the present invention and having a refractive index exceeding 2.1, the stability at the time of melting the glass tends to decrease. In that case, the stability is greatly improved by balancing RO to a predetermined content with respect to the total content of Bi ₂ O ₃ . Therefore, the value of (total content of RO) / (content of Bi ₂ O ₃ ) is preferably 0.005, more preferably 0.010, most preferably 0.015, and preferably 0.00. The upper limit is 100, more preferably 0.090, and most preferably 0.080.

The ZnO component is a component that is effective for improving glass stability, melting property, and high dispersion. However, if the amount is too large, the glass stability tends to be lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The BaO component is a component effective for improving the glass stability and increasing the refractive index. However, if the amount is too large, the chemical durability is lowered and the glass stability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The SrO component is a component having an effect of keeping the glass at a high refractive index and high dispersion, but if the amount is too large, the glass stability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The CaO component is a component effective for improving the glass stability and reducing the dispersion, but if the amount is too large, the glass stability tends to be lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The MgO component is a component having an effect of reducing the dispersion, but if the amount is too large, the devitrification resistance may be lowered in the press temperature range. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

Rn ₂ O component (Rn is one or more selected from the group consisting of Li, Na, K, and Cs) can be contained in order to improve the melting property of the glass and lower the glass transition point, but excessively contained Doing so tends to lower the chemical durability. In the present invention, the desired optical glass can be obtained without including the Rn ₂ O component, but in order to obtain the above effect, the total content of Rn ₂ O is preferably 0.1%, more preferably 0.8. The lower limit is 5%, most preferably 1%, preferably 15%, more preferably 10%, and most preferably 5%.

The Li ₂ O component is a component that is effective for lowering Tg, improving glass stability, and improving meltability. However, if the amount is too large, chemical durability tends to decrease. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The Na ₂ O component is an effective component for lowering Tg and improving meltability. However, if the amount is too large, glass stability and chemical durability are likely to be reduced. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The K ₂ O component is a component having an effect of low dispersion and low Tg. If the amount is too large, the glass stability and chemical durability are likely to be lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The Cs ₂ O component is a component having an effect of lowering the Tg. However, when the amount is too large, the glass stability is lowered and the chemical durability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The total content of the RO and Rn ₂ O components is preferably 0.1% or more, more preferably 1% for the purpose of improving the stability of the glass, adjusting the optical constant, lowering the glass transition point, and the like. More than 1.5%, and most preferably 1.5% or more. Further, if the total content of the RO and Rn ₂ O components is too large, the liquid phase temperature tends to increase and the chemical durability tends to decrease, so the total content is preferably 15%, more preferably 10 %, Most preferably 5%.

B ₂ O ₃ , SiO _2, and Al ₂ O ₃ are components useful as glass forming components, and are components that can improve transmittance, improve viscosity with respect to liquidus temperature, and improve chemical durability. . Therefore, the total content of one or more of these components is preferably 0.1% or more, more preferably 2% or more, and further preferably 4% or more. However, if the total content of these components is too large, Tg tends to be high, and the upper limit is preferably 15%, more preferably 13%, and most preferably 10%. Further, when production is carried out in this range of composition, since the glass has a low liquidus temperature and is stable, the yield during production can be improved.

The B ₂ O ₃ component is a useful component for improving the glass stability, but if the amount is too large, the glass stability tends to deteriorate. Even if the B ₂ O ₃ component is not contained, it is possible to obtain the objective optical glass of the present invention, but in order to achieve the above effect, it is preferable to contain more than 0%, more preferably. The lower limit is 0.1%, most preferably 0.2%, preferably 15%, more preferably 13%, and most preferably 10%.

The SiO ₂ component is a component useful for improving the glass stability and increasing the viscosity of the glass. However, if the amount is too large, the refractive index (nd) tends to be small. Even if the SiO ₂ component is not contained, it is possible to obtain the objective optical glass of the present invention. However, in order to achieve the above effect, it is preferable to contain more than 0%, preferably 0.1%. %, More preferably 0.2% is the lower limit, preferably 15%, more preferably 13%, and most preferably 10%.

The Al ₂ O ₃ component is a useful component for improving the glass stability and improving the chemical durability and mechanical strength. However, if the amount is too large, the glass stability tends to deteriorate. Therefore, the upper limit is preferably 15%, more preferably 13%, and most preferably 10%. Al ₂ O ₃ may not be contained.

The TiO ₂ component is an optional component effective for obtaining a high refractive index and high dispersion. However, if the amount is too large, the transmittance is lowered and the glass stability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The Nb ₂ O ₅ component is an optional component effective for maintaining a high refractive index of the glass, but if the amount is too large, the glass stability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The WO ₃ component is an optional component effective for maintaining high dispersion of the glass, but if the amount is too large, the glass stability is lowered and the transmittance is easily deteriorated. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The Ta ₂ O ₅ component is an optional component effective for maintaining a high refractive index, but if the amount is too large, the stability of the glass is deteriorated. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The ZrO ₂ component is an optional component effective as a component for improving chemical durability, but if the amount is too large, the stability of the glass is deteriorated. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

Each component of Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , and Yb ₂ O ₃ is effective in improving the chemical durability of glass and maintaining a high refractive index, and can be optionally added. Although it is a component, if the amount thereof is large, the devitrification resistance tends to be lowered. Therefore, the upper limit of the total amount of the above components is preferably 15%, more preferably 10%, and most preferably 5%. In each component, there is no problem as long as it is 10% or less.

The P ₂ O ₅ component is a component that is effective in improving the glass stability and can be optionally added. However, if the amount is too large, the phase separation tendency of the glass becomes strong. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%. More preferably, it is not included.

The Sb ₂ O ₃ component is a defoaming agent, a glass redox adjustment effect, and a high dispersion effect, and can be added arbitrarily. If the amount is too large, the meltability deteriorates and the transmittance decreases. Make it easier. Therefore, the upper limit is preferably 3%, more preferably 2%, and most preferably 1%.

The GeO ₂ component is an effective component for improving the coloration of the glass and improving the glass stability. However, since it is expensive, the upper limit is preferably 15%, preferably 10%, and preferably 5%. It is preferable that More preferably, it is not included.

F has an effect of increasing the meltability of the glass, but is a component that can be optionally added to rapidly decrease the refractive index and deteriorate the devitrification resistance. Therefore, when the total amount of F in which a part or all of the oxide is fluoride-substituted is expressed as mass% when calculated as F atoms based on 100 mass% of the oxide-based composition, the upper limit is 10 %, More preferably 5%, and most preferably 1%. More preferably not.

<About ingredients that should not be included>
In this invention, another component can be added as needed in the range which does not impair the characteristic of the glass of this invention. However, even when each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo excluding Ti is contained alone or in combination with a small amount, the glass is colored and visible. Causes absorption at specific wavelengths in the region. Therefore, it is preferable that the optical glass using a wavelength in the visible region does not contain substantially. Here, “substantially free” means that it is not contained artificially unless it is mixed as an impurity.

The Th component can be contained for the purpose of increasing the refractive index or improving the stability as glass, and the Cd and Tl components can be contained for the purpose of reducing the Tg. However, since each component of Th, Cd, Tl, and Os tends to be refrained from being used as a harmful chemical substance component in recent years, not only the glass manufacturing process, but also the processing process and the disposal after commercialization are used. Countermeasures are required. Therefore, it is preferable not to include substantially when the influence on the environment is emphasized.

Since the lead component needs to take measures for environmental measures when manufacturing, processing, and disposing of the glass, the cost becomes high and the lead component should not be contained in the glass of the present invention.

As ₂ O ₃ component is a component that is used to improve the clarity of glass melting, but it is necessary to take measures on environmental measures when manufacturing, processing, and disposing of glass. It is not preferable to include As ₂ O ₃ in the glass of the present invention.

The glass composition of the present invention cannot be expressed directly in the description of mol% because the composition is expressed by mass%, but exists in the glass composition satisfying various properties required in the present invention. The composition of each component in terms of mol% takes the following values in terms of oxide equivalent composition.
Bi ₂ O ₃ 40% or more,
Exceeding SiO ₂ 0 and 30% or less,
B ₂ O ₃ 0 to 50% or less, and Al ₂ O ₃ 0-20% and / or TiO ₂ 0-20 and / or Nb ₂ O ₅ 0-20% and / or WO ₃ 0-10% and / or Or Ta ₂ O ₅ 0-10% and / or ZrO ₂ 0-10% and / or ZnO 0-20% and / or MgO 0-30% and / or CaO 0-40% and / or SrO 0-40% and / or BaO 0 to 40% and / or Li ₂ O 0 to 30% and / or Na ₂ O 0 to 30% and / or K ₂ O 0 to 30% and / or Y ₂ O ₃ 0~20% and And / or La ₂ O ₃ 0-20% and / or Gd ₂ O ₃ 0-20% and / or Yb ₂ O ₃ 0-20% and / or P ₂ O ₅ 0-50% and / or Sb ₂ O ₃ 0 to 1% and / or GeO ₂ 0 to 20% and / or CeO ₂ 0-5% and / or TeO ₂ 0-5% and / or F 0-10% and / or

Next, the physical properties of the optical glass of the present invention will be described.
The optical glass of the present invention has a refractive index (n _d ) of preferably 2.10, more preferably 2.12, and most preferably 2.15 from the viewpoint of usefulness in optical design. The upper limit is 40, more preferably 2.35, and most preferably 2.30.

In addition, the optical glass of the present invention has an Abbe number (ν _d ) of preferably 10, more preferably 11, most preferably 12 as a lower limit, preferably 20, and more preferably 19 from the viewpoint of usefulness in optical design. Most preferably, the upper limit is 18.

In the optical glass of the present invention, when the glass transition point (Tg) becomes too high, as described above, when precision press molding is performed, the mold and the mold film are likely to deteriorate. Therefore, Tg of the optical glass of the present invention is preferably 500 ° C., more preferably 450 ° C., and most preferably 400 ° C.

The optical glass of the present invention is precision press-molded and typically can be used for lens, prism and mirror applications. As described above, the optical glass of the present invention can be used as a preform material for press molding, or the molten glass can be directly pressed. When used as a preform material, the production method and precision press molding method are not particularly limited, and known production methods and molding methods can be used. As a method for producing a preform material, for example, a glass gob forming method described in JP-A-8-319124, an optical glass manufacturing method described in JP-A-8-73229, and a preform material directly from molten glass such as a manufacturing apparatus are used. The strip material may be manufactured by cold working.

In addition, when manufacturing a preform by dripping molten glass using the optical glass of the present invention, if the viscosity of the molten glass is too low, the glass preform tends to have striae. It becomes difficult to cut glass by tension.

Therefore, for high quality and stable production, the logarithmic log η value of the viscosity (dPa · s) at the liquidus temperature is preferably 0.3 to 2.0, more preferably 0.3 to 1.8, Most preferably, it is in the range of 0.3 to 1.6.

Since the optical glass of the present invention is used as a lens for a digital camera or a digital video camera, it is preferable that the light transmittance is high. In particular, a wavelength at a spectral transmittance of 5% (10 mm thickness) including reflection loss ( λ5) is preferably 470 nm, more preferably 460 nm, and most preferably 455 nm.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to the following.

In the composition shown in Table 1, the raw materials were weighed so as to have a glass weight of 400 g and mixed uniformly. After melting at 750 ° C. to 950 ° C. for 2 to 3 hours using a quartz crucible or a metal crucible, the temperature was lowered to about 700 to 600 ° C. and kept warm for about 1 hour, and then cast into a mold to produce glass. Table 1 shows the obtained glass characteristics.

The refractive index (nd) and Abbe number (νd) were measured based on Japan Optical Glass Industry Association Standard JOGIS 01-2003. The annealing conditions were a slow cooling furnace with a slow cooling rate of -25 ° C / hr.

The wavelength (λ5) having a transmittance of 5% including reflection loss was measured by an apparatus and a measuring method according to JIS Z 8722.

About the glass transition point (Tg), the obtained optical glass was made into a powder form and measured using a differential thermal analyzer (STA 409 CD manufactured by Netchgeretebau). The sample particle size was 425 to 600 μm, and the heating rate was 10 ° C./min.

The glass of the example of the present invention can obtain an optical glass having a refractive index (nd) of 2.1 or more and a sufficiently low glass transition point (Tg). The glass of the comparative example is a general high refractive index glass in terms of optical characteristics.

In Examples 1 to 20, an optical glass having a refractive index (nd) of 2.1 or more and a sufficiently low glass transition point (Tg) could be obtained stably. On the other hand, Comparative Example 1 has a refractive index of 2.1 or less, insufficient glass stability, and it is difficult to achieve a high refractive index due to a higher Bi ₂ O ₃ content. Comparative Example 2 had a refractive index of 2.1 or less and a large value of transmittance λ5, which was insufficient for use as optical glass.

Claims (6)

Containing 85% or more and 91.28% or less of Bi ₂ O ₃ in mass% based on oxide;
B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ are contained in a total content of 2% to 10% ,
RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, Mg) 1% or more and 5% or less,
Refractive index (nd) is 2.15 or more, Abbe number (νd) is 20 or less,
An optical glass characterized in that the wavelength at a spectral transmittance of 5% (10 mm thickness) including reflection loss is 470 nm or less ( excluding those containing 1 mol% or more of Ga ₂ O ₃ ) .   The optical glass according to claim 1, wherein the glass transition point (Tg) is 500 ° C. or less. % By mass based on oxide,
ZnO 0-5 %,
BaO 0-5 %,
SrO 0-5 %,
CaO 0 to 5%,及Beauty <br/> MgO 0~ 5%,
L i ₂ O 0~ 10%,
Na ₂ O 0-10 %,
K ₂ O 0~ 10%,及Beauty <br/> Cs ₂ O _0~ 10%,
However _Rn 2 O (Rn is Li, Na, K, one or more selected from the group consisting of Cs) total content 0-10% less,及Beauty <br/> B ₂ O ₃ 0-10%,
SiO ₂ 0~ 10%,
Al ₂ O ₃ 0-10 %,
TiO ₂ 0-10 %,
Nb ₂ O ₅ 0~ 10%,
WO ₃ 0~ 10%,
Ta ₂ O ₅ 0~ 10%,
ZrO ₂ 0-10 %,
Y ₂ O ₃ 0-10 %,
La ₂ O ₃ 0-10 %,
Gd ₂ O ₃ 0-10 %,
Yb ₂ O ₃ 0-10 %,
P ₂ O ₅ 0~ 10%,
Sb ₂ O ₃ 0~ _3%, 及Beauty _{<br/> Ge 2 O 3 0~ 10%} , of the total amount the oxidation of F that some or all the fluoride replacement of the oxide containing the components 3. The optical glass according to claim 1, wherein an upper limit value expressed by mass% when calculated as F atoms based on 100 mass% of an object standard composition is 10% or less. A precision press-molding preform comprising the optical glass according to any one of claims 1 to 3 . An optical element comprising the optical glass according to any one of claims 1 to 3. An optical element formed by precision pressing the preform of claim 4 .