JP2008273750A - Optical glass - Google Patents

Abstract

A B ₂ O ₃ —La ₂ O ₃ —ZnO—WO ₃ —TeO ₂ -based glass composition having excellent devitrification resistance and an optical constant (refractive index, An optical glass suitable for precision mold press formation having an Abbe number and a low glass transition point is provided at a low cost.
A in mole percent on the oxide _basis, B 2 _{O 3} component 25 to 60%, WO ₃ ingredient 1 to 40%, characterized in that it contains TeO ₂ component from 0.2 to 60%. Furthermore, the Nb ₂ O ₅ component content is preferably 5%, preferably less than 1%, and the Ga ₂ O ₃ component content is preferably less than 1%. The optical glass has an optical constant of refractive index (nd) of 1.80 to 2.10, Abbe number (νd) of 18 to 40, and glass transition point (Tg) of 680 ° C. or lower.
[Selection figure] None

Description

  The present invention relates to an optical glass, and more particularly to an optical glass suitable for precision press molding (mold press molding) having a high refractive index and a high dispersion characteristic and having a low glass transition point.

  In recent years, with the advent of digital cameras, with the rapid progress of higher integration and higher functionality of devices that use optical systems, the demand for higher precision, lighter weight, and smaller size for optical systems is also increasing. In order to realize the demand, optical design using an aspheric lens is becoming mainstream. Therefore, in order to stably supply a large amount of aspherical lenses using high-performance glass at a low cost, a molding technology that directly forms an optical surface without the need for grinding and polishing processes has attracted attention, and high functionality The demand for optical glass suitable for molding having high refractive index / low dispersion / high refractive index / high dispersion (for example) continues to increase year by year.

  In precision press molding of glass, a glass mold preform (glass preform) is pressure-molded at a high temperature using a mold having a cavity with a predetermined shape, so that the final product shape or shape and surface accuracy very close to it are obtained. According to precision press molding, a molded product having a desired shape can be produced with high productivity. For this reason, various optical glass parts such as spherical lenses, aspherical lenses, and diffraction gratings are currently manufactured by precision press molding. Of course, in order to obtain an optical glass part by precision press molding, it is necessary to press-mold the glass preform at a high temperature as described above, so that the mold used for the press is exposed to a high temperature, And high pressure is applied. For this reason, for glass preforms, the glass transition point can be made as low as possible from the viewpoint of suppressing damage to the mold itself and the release film provided on the inner surface of the mold due to the high temperature environment of press molding. It is desired. In addition, even when precision preformed glass preform material that has been devitrified, devitrification does not disappear, and glass molded products containing devitrification cannot be used as optical elements such as lenses. The glass of the glass preform material used for is required to be a glass having high devitrification resistance.

  Conventionally, optical glass with high refractive index and high dispersibility is typically a composition system containing a large amount of lead oxide, and it is used for precision mold press molding because of its high glass stability and low glass transition point. It has been. For example, Patent Document 1 discloses an optical glass for precision mold presses that contains a large amount of lead oxide.

  However, since the environment for precision mold press molding is maintained in a reducing atmosphere to prevent oxidation of the mold, if lead oxide is contained in the glass component, reduced lead is deposited from the glass surface. However, there is a problem that this adheres to the mold surface and the precision surface of the mold cannot be maintained. Further, lead oxide is harmful to the environment, and it has been desired not to contain it.

On the other hand, various glasses containing TeO ₂ component and the like have been developed as optical glasses for press molding having a high refractive index and high dispersibility and containing no lead oxide. For example, Patent Document 2 and Patent Document 3 Patent Document 4, Patent Document 5, and the like.
Japanese Patent Laid-Open No. 01-308443 JP 2004-43294 A JP 2005-154251 A JP 2006-182577 A JP 2006-131450 A

However, the glass disclosed in Patent Document 2 contains a TeO ₂ component of 20 mol% or more and has a low glass transition point, but these glasses are mainly composed of _two components of a TeO ₂ component and a ZnO component, Since the total amount of both components exceeds 70 mol%, there are disadvantages that the devitrification resistance and chemical durability are low and that the stability of the glass is low because it does not contain any WO ₃ component. The glass disclosed in Patent Document 3 is a B ₂ O ₃ —ZnO—La ₂ O ₃ —Ga ₂ O ₃ based optical glass, and further contains 0 to 20 mol% of TeO ₂ component. The glass transition point is low and the refractive index and transmittance are high. However, in order to obtain high functions such as glass stabilization, an expensive Ga ₂ O ₃ component is contained instead of the WO ₃ component. The glass disclosed in Patent Document 4 is an optical glass based on B ₂ O ₃ —ZnO—La ₂ O ₃ —TeO ₂ —Nb ₂ O _{5 and} contains 10 to 40 mol% of a TeO ₂ component. The glass transition point is low and the refractive index and transmittance are high. However, since the B ₂ O ₃ component content is 30 mol% or less, the devitrification resistance is insufficient, and further, Nb ₂ O _{Since 5} components are contained in 5 to 20 mol%, the meltability of the glass is deteriorated and the devitrification property is easily increased. Further, the glass disclosed in Patent Document 5 contains an expensive Ga ₂ O ₃ component as an essential component in order to stabilize the glass and obtain a high refractive index.

The present invention is a B ₂ O ₃ —La ₂ O ₃ —ZnO—WO ₃ —TeO ₂ -based glass composition having excellent devitrification resistance and an optical constant (refractive index) required for an aspheric lens or the like. The present invention is to provide a novel optical glass suitable for precision mold press molding having a low glass transition point and a low glass transition point.

In order to solve the above-mentioned problems, the present inventor has conducted earnest test research, and as a result, the B ₂ O ₃ component, the TeO ₂ component, and the WO ₃ component are within a predetermined range, so as not to contain lead. It is possible to obtain an optical glass having an optical constant in the above-mentioned specific range and has a low glass transition point capable of precision press molding, so that a glass preform material suitable for precision press molding can be easily obtained. The headline and the present invention were completed.

  More specifically, the present invention provides the following.

(1) in mole percent on the oxide _basis, B 2 _{O 3} component 25 to 60%, WO ₃ ingredient 1 to 40%, optical glass containing TeO ₂ component from 0.2 to 60%.

According to the aspect of (1), it is excellent in the meltability, stability, and devitrification resistance of glass, and has an optical glass having a high refractive index and high dispersion and a low glass transition point. This is because the optical glass of the present invention is effective in increasing the devitrification property of the glass and the viscosity with respect to the liquidus temperature, and contains a large amount of B ₂ O ₃ component which is an indispensable component as a glass forming oxide. In addition, it contains WO ₃ component and TeO ₂ component, which are effective for lowering the glass transition point, contributing to the improvement of glass stability, increasing the refractive index, and giving high dispersion as essential components. It is.

(2) The optical glass according to (1), wherein the Nb ₂ O ₅ component content is less than 5% in terms of mol% based on oxide.

According to the aspect of (2), since Nb ₂ O ₅ component is not contained or less than 5% even if it is contained, high refractive index, high dispersion, anti-resistance without deteriorating the meltability of the glass. Glass excellent in devitrification can be obtained.

(3) The optical glass according to (1) or (2), wherein the content of the Ga ₂ O ₃ component is less than 1% in terms of mol% based on the oxide.

(3) According to the aspect, since even contain or not contain Ga ₂ O ₃ is less than 1%, it is possible to obtain a low cost glass.

(4) The optical glass according to any one of (1) to (3), containing 1 to 35% of a La ₂ O ₃ component and / or 1 to 40% of a ZnO component in mol% based on an oxide.

According to the aspect of (4), the meltability, stability and devitrification resistance of the glass are further improved, the glass has a wider refractive index and dispersion, and the glass transition point is lower, and the precision press formability is improved. It becomes an excellent optical glass. In addition to the glass components (1) to (3) above, this further increases the refractive index of the glass and lowers the La ₂ O ₃ component and / or the glass transition point effective for imparting a wide dispersion. This is because it contains a ZnO component that is effective for the above.

(5) in mole percent on the oxide basis, from the _Bi 2 _{O 3} component containing 0-30%, the total amount of the TeO ₂ component and _Bi 2 _{O 3} component is 0.2 to 60% (1) ( The optical glass according to any one of 4).

According to the aspect of (5), the TeO ₂ component improves the stability of the glass and lowers the glass transition point. However, if it is too much, the stability of the glass is lowered and the chemical durability is also lowered. To do. Further, the Bi ₂ O ₃ component is a component that has the effect of improving the stability of the glass, increasing the refractive index, increasing the dispersion, and lowering the glass transition point. Therefore, an optical glass having a low glass transition point and excellent chemical durability and devitrification resistance can be obtained.

(6) mol% on oxide basis,
Rn ₂ O component (Rn represents one or more selected from the group consisting of Li, Na, K, Cs) 0 to 15%, and / or RO component (R consists of Ba, Sr, Ca, Mg) One or more selected from the group) 0-20%, and / or SiO ₂ component 0-20%, and / or GeO ₂ component 0-20%, and / or P ₂ O ₅ component 0-10%, and / or _Al 2 _{O 3} component 0-20%, and / or _{Gd 2 O 3 + Y 2 O} 3 + Yb 2 O 3 component 0-20%, and / or TiO ₂ component + _Nb 2 O Less than 1% of ₅ components and / or 0-10% of Ta ₂ O ₅ components and / or 0-10% of ZrO ₂ components and / or 0-5 of Sb ₂ O ₃ components + As ₂ O ₃ components %
The optical glass according to any one of (1) to (5).

According to an aspect of the (6), Rn ₂ O component (Rn is Li, Na, K, indicating one or more members selected from the group consisting of Cs) and RO component (R is Ba, Sr, Ca, and Mg By including a component such as one or more selected from the group consisting of the above group, the melting property of the glass is further improved and the glass transition point is lower. Further, components such as SiO ₂ component, GeO ₂ component, and P ₂ O ₅ component are glass-forming oxides, and are particularly useful for obtaining highly transparent glass without devitrification. Y ₂ O ₃ component, Components such as Gd ₂ O ₃ component, Yb ₂ O ₃ component, Ta ₂ O ₅ component, and ZrO ₂ component are effective in improving the refractive index of the glass and adjusting the dispersion. Further, the Al ₂ O ₃ component is effective in improving chemical durability and improving mechanical strength. Further, the TiO ₂ component and the Nb ₂ O ₅ component are effective for increasing the refractive index of the glass and achieving high dispersion. However, if the amount is too large, the meltability and stability of the glass are deteriorated. In addition, Sb ₂ O ₃ and / or As ₂ O ₃ components can be optionally added for glass defoaming, but As ₂ O ₃ components can be used to produce, process, and dispose of glass. It is necessary to take measures for environmental measures. Therefore, according to the aspect of (6), it is excellent in the meltability, stability, devitrification resistance, chemical durability, etc. of the glass, further improving the refractive index and high dispersion of the glass, and the glass transition point. It becomes a lowered optical glass.

  (7) The optical glass according to any one of (1) to (6), wherein the refractive index (nd) is 1.80 to 2.10 and the Abbe number (νd) is 18 to 40.

  According to the aspect of (7), since it is a high refractive index and high dispersion glass having a refractive index and an Abbe number in the above ranges, the number of lenses is reduced, and the weight and size of the device using the optical glass are reduced. be able to.

  (8) Optical glass in any one of (1) to (7) whose glass transition point is 680 degrees C or less.

  According to the aspect of (8), since a glass transition point is 680 degrees C or less, precision press molding is possible at a comparatively low temperature. For this reason, the damage by the high temperature environment of press molding to the mold used for precision press molding is suppressed, and damage to the release film provided on the inner surface of the mold is also suppressed.

  (9) The optical glass according to any one of (1) to (8), wherein a wavelength of 70% transmittance in a glass having a thickness of 10 mm is 500 nm or less.

  According to the aspect of (9), since the wavelength which shows the transmittance | permeability of 70% in glass with a thickness of 10 mm is 500 nm or less, it has a high transmittance | permeability in a visible region. Therefore, it can be suitably used as an optical glass.

According to the present invention, an optical glass having an optical constant having a refractive index (nd) of 1.80 to 2.10 and an Abbe number (νd) of 18 to 40 can be obtained. Since a point is 680 degrees C or less, it is suitable for the glass preform material used for precision press molding, and precision press molding. Compared to conventional optical glass containing almost no Ga ₂ O ₃ component, it has high stability, high dispersibility, high transparency in the visible region, and satisfies recent optical design requirements. Can do.

  Hereinafter, the present invention will be specifically described.

  The components that can be contained in the optical glass of the present invention will be described. Hereinafter, unless otherwise specified, the content of each component is expressed in mol%.

The optical glass of the present invention is 25 to 60% of _B 2 _{O 3} component as an essential component, the WO ₃ ingredient 1 to 40%, a TeO ₂ component from 0.2 to 60%, each component of the oxide composition in terms of contains. Preferably, the content of Nb ₂ O ₅ component is less than 5%, more preferably less than 1%, most preferably not. Further, the content of Ga ₂ O ₃ component is preferably less than 1%, more preferably not contained. Further, it preferably contains 1 to 35% La ₂ O ₃ component and / or 1 to 40% ZnO component and / or 0 to 30% Bi ₂ O ₃ component. More preferably, an Rn ₂ O component (Rn represents one or more selected from the group consisting of Li, Na, K, and Cs) as an optional component is 0 to 15%, and / or an RO component (R is Ba, Sr) , 0 or 20% selected from the group consisting of Ca and Mg), and / or 0 to 20% of SiO ₂ component, and / or 0 to 20% of GeO ₂ component, and / or 0 to 10% P ₂ O ₅ component and / or 0 to 20% Al ₂ O ₃ component and / or 0 to 20% Gd ₂ O ₃ + Y ₂ O ₃ + Yb ₂ O ₃ component and / or TiO ₂ component + Nb ₂ O ₅ component is less than 1%, and / or Ta ₂ O ₅ component is 0-10%, and / or ZrO ₂ component is 0-10%, and / or Sb ₂ O ₃ component + As ₂ O ₃ to 0-5%
More preferably, the refractive index (nd) has an optical constant in the range of 1.80 to 2.10 and the Abbe number (νd) in the range of 18 to 40, and more preferably the glass transition point is 680 ° C. or less. It is an optical glass. Moreover, the wavelength which shows the transmittance | permeability of 70% in the glass of thickness 10mm is 500 nm or less.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In the present specification, the content of each component is expressed in mol% unless otherwise specified. Here, the “oxide standard” means that the oxide, nitrate, etc. used as a raw material of the glass component of the present invention are all decomposed and changed into oxides when melted, and the mass of the generated oxide Is a composition in which each component contained in the glass is represented with the total of 100 mol%.

<About essential and optional components>
In the optical glass of the present invention, the B ₂ O ₃ component is an indispensable component as a glass-forming oxide, and also has an effect of improving the devitrification of the glass and increasing the viscosity at the liquidus temperature. . However, if the amount is too small, the devitrification resistance tends to decrease, and if the amount is too large, the refractive index tends to be low. Therefore, the lower limit is preferably 25%, more preferably 30%, most preferably 35%, and the upper limit is preferably 60%, more preferably 55%, most preferably 50%.

The WO ₃ component is an essential component effective for improving the stability of the glass, increasing the refractive index, contributing to high dispersion, and lowering the glass transition point. However, if the amount is too small, the desired effect is achieved. Is difficult to obtain, and if the amount is too large, the phase separation of the glass tends to increase. Therefore, the lower limit is preferably 1%, more preferably 3%, most preferably 5%, and the upper limit is preferably 40%, more preferably 35%, most preferably 30%.

The TeO ₂ component is an essential component that has the effects of improving the stability of the glass, lowering the glass transition point, and increasing the refractive index. However, if the amount is too large, the glass tends to be colored black and the stability tends to decrease. In addition, since the thermal expansion coefficient of glass tends to increase, the glass tends to break during precision molding. Further, when glass is melted using a platinum crucible as a container, the glass solution is likely to erode platinum. Therefore, there is a concern about the risk of an accident that a hole is opened in the container and the molten glass flows out. On the other hand, if the amount is too small, it is difficult to obtain the above effect. Therefore, the upper limit of the content is preferably 60%, more preferably 40%, most preferably less than 30%, and the lower limit is preferably 0.2%, more preferably 1%, most preferably 3%. be able to.

The La ₂ O ₃ component is an optional component that contributes to improving the stability of the glass, and further increases the refractive index and has a wide dispersion. However, if the amount is too small, these effects are insufficient, and if the amount is too large, the devitrification resistance tends to deteriorate rapidly. Therefore, in order to easily obtain the desired effect (optical constant and good devitrification resistance), the lower limit is preferably 1%, more preferably 3%, most preferably 5%, and the upper limit is preferably 35. %, More preferably 30%, most preferably 25%.

  The ZnO component is an optional component that has a large effect of improving the stability of the glass and lowering the glass transition point. However, if the amount is too large, it becomes difficult to maintain the target refractive index, and resistance to devitrification It is easy to get worse. If the amount is too small, it is difficult to obtain a desired effect. Therefore, in order to further lower the glass transition point while maintaining good devitrification resistance, the lower limit is preferably 1%, more preferably 3%, most preferably 6%, and the upper limit is preferably 40%. , More preferably 30%, most preferably less than 25%.

The Bi ₂ O ₃ component is an optional component that has the effect of improving the stability of the glass, increasing the refractive index, increasing the dispersion, and lowering the glass transition point. However, if the amount is too large, the glass stability tends to be impaired. Therefore, the upper limit of the content is preferably 30%, more preferably 20%, and most preferably 15%.

Further, since the Bi ₂ O ₃ component functions similarly to TeO ₂ as described above, it is preferable to introduce it in the form of replacing the TeO ₂ component. In order to obtain a stable glass, the lower limit of the total amount of both components is preferably 0.2%, more preferably 3%, most preferably 5%, and the upper limit is preferably 60%, more preferably 50%, most Preferably it can be contained as 45%.

Rn ₂ O (Rn represents one or more selected from the group consisting of Li, Na, K, and Cs) has an effect of significantly lowering the glass transition point and promoting melting of the mixed glass raw material. It is an optional component. However, if the amount is too large, the devitrification resistance tends to deteriorate rapidly. Therefore, in order to maintain a good glass transition point or devitrification resistance, the upper limit of the content is preferably 15%, more preferably 12%, and most preferably 8%. .

  RO (R represents one or more selected from the group consisting of Ba, Sr, Ca, and Mg) is an optional component that is effective in improving the meltability, devitrification resistance, and chemical durability of glass It is. However, if the amount is too large, the stability of the glass tends to deteriorate rapidly. Therefore, in order to easily maintain the stability of the glass, the upper limit of the content is preferably 20%, more preferably 15%, and most preferably 10%.

The SiO ₂ component is a component that constitutes the skeleton of the glass, and is an optional component that has the effect of improving devitrification resistance and chemical durability and extending the working range. However, if the amount is too large, the stability of the glass decreases, so the upper limit of the content is preferably 20%, more preferably 15%, and most preferably 10%.

The GeO ₂ component is effective in improving the stability and refractive index of the glass, and is an optional component that contributes to high dispersion, and is more preferably introduced into the glass in a form that replaces a part of B ₂ O ₃ . However, since it is expensive, in order to make it easy to maintain the glass transition point at 500 to 700 ° C., the upper limit of the content is preferably 20%, more preferably 15%, and more preferably 10%. Most preferably.

The P ₂ O ₅ component is an optional component that is effective for improving the stability of the glass and lowering the glass transition point. However, when the amount is too large, the phase separation of the glass tends to increase. Therefore, the upper limit of the content is preferably 10%, more preferably 8%, and most preferably 5%.

Al ₂ O ₃ is an optional component effective for improving chemical durability and improving mechanical strength. However, if the amount is too large, the meltability of glass deteriorates and devitrification increases. It tends to increase the glass transition point. Therefore, the upper limit of the content is preferably 20%, more preferably 10%, and most preferably 5%.

The Y ₂ O ₃ component and / or the Gd ₂ O ₃ component and / or the Yb ₂ O ₃ component are optional components that increase the refractive index of the glass and are effective in adjusting the dispersion. However, if the amount is too large, the devitrification resistance of the glass tends to deteriorate. Therefore, in order to easily maintain good devitrification resistance while maintaining the desired optical constant in the present invention, the upper limit of the total amount is preferably 20%, more preferably 15%. Preferably, 10% is most preferable.

The Ta ₂ O ₅ component is an optional component that is effective in increasing the refractive index of glass and improving chemical durability. However, if the amount is too large, the stability of the glass tends to decrease, and the glass transition point tends to increase. Therefore, in order to easily maintain good chemical durability and stability while maintaining the desired optical constant in the present invention, the upper limit of the content is preferably 10%, and is preferably 8%. Is more preferable, and 5% is most preferable.

The ZrO ₂ component is an optional component that is effective in increasing the refractive index of the glass and improving the chemical durability, but if introduced in a large amount, the stability of the glass tends to decrease, so the upper limit of its content Is preferably 10%, more preferably 8%, and most preferably 5%.

The Nb ₂ O ₅ component is an effective component for increasing the refractive index of glass, contributing to high dispersion, and improving the devitrification property of glass. However, if the amount is too large, the melting property of glass is increased. It tends to get worse. Therefore, it is preferably not contained, but even if contained, it is less than 5%, more preferably less than 1%.

The Ga ₂ O ₃ component is an effective component for improving the refractive index, but is expensive and easily deteriorates the stability of the glass. Therefore, it is preferable not to contain, but even if it contains, less than 1% is preferable.

The TiO ₂ component and / or the Nb ₂ O ₅ component is an optional component effective to increase the refractive index of the glass, contribute to high dispersion, and improve the devitrification property and chemical durability of the glass. If the amount is too large, the meltability and stability of the glass tend to be deteriorated. Accordingly, the amount is preferably less than 1% even if contained.

Sb ₂ O ₃ and / or As ₂ O ₃ components can be optionally added for defoaming the glass melt, but up to 5% is sufficient. In particular, it is preferable not to include the As ₂ O ₃ component because it is necessary to take measures for environmental measures when manufacturing, processing, and discarding the glass.

<About ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention will be described.

  The lead component is a component that is easy to fuse with the mold at the time of precision press molding, and there are not only measures for environmental measures, from glass processing such as polishing to glass disposal, as well as glass manufacturing. Necessary. Thus, since there is a problem that it is a component with a large environmental load, it is preferable not to make it contain in the optical glass of this invention.

  Both the cadmium component and the thorium component are harmful components to the environment and have a very large environmental load, and therefore should not be contained in the optical glass of the present invention.

  Furthermore, in the optical glass of the present invention, coloring components such as V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Eu, Nd, Sm, Tb, Dy, and Er have desired characteristics as optical glass. Since it is easy to damage, it is preferable not to contain. However, the term “not contained” as used herein means that it is not contained artificially unless it is mixed as an impurity.

<Physical properties>
Next, the physical properties of the optical glass of the present invention will be described.

  The optical glass of the present invention is used for applications requiring an optical constant in the above range, and further used as a glass preform material for heat softening and obtaining a glass molded product by precision press molding. Therefore, in order to suppress damage and deterioration of the mold used at this time, maintain a high-precision molding surface of the mold for a long time, and enable precision press molding at a low temperature, the glass transition point is as low as possible. It is desirable to have Therefore, a desired glass transition point is realized by using the composition in the specific range.

  The glass transition point of the optical glass of the present invention is preferably 680 ° C. or lower. Furthermore, the upper limit is 680 ° C., preferably 650 ° C., most preferably 620 ° C., and the lower limit is preferably 450 ° C., more preferably 480 ° C., and most preferably 500 ° C. The reason is that if the glass transition point is too low, the chemical durability tends to deteriorate and the devitrification resistance tends to decrease at the same time, and as a result, stable production tends to be difficult. On the other hand, if the glass transition point becomes too high, moldability in mold press molding tends to deteriorate.

  In the optical glass of the present invention, when performing mold press molding, there is a correlation with the glass yield point (Ts) in addition to the upper limit temperature of the mold press and the glass transition point, and the temperature of the glass yield point (Ts) is low. The lower the value, the lower the progress of surface oxidation of the mold, which is preferable from the viewpoint of the life of the mold. For this reason, the glass yield point (Ts) is preferably 720 ° C. or less, more preferably 690 ° C. or less, and most preferably 660 ° C. or less. Here, the glass yield point (Ts) is a temperature at which when the glass is heated, the elongation of the glass stops and then starts to shrink. In the present invention, the temperature rise rate is 8 ° C. / Measured in min.

  As described above, the optical glass of the present invention can be used as a glass preform material for press molding, or a molten glass can be directly pressed. When using as a glass preform material, the manufacturing method and the hot forming method are not particularly limited, and known manufacturing methods and forming methods can be used. As a method for producing a glass 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 glass preform directly from molten glass such as a manufacturing apparatus are used. The material can also be manufactured, or the strip material can be manufactured by cold working.

  The hot forming method for the glass preform material is not particularly limited, and for example, a method such as the optical element forming method described in JP-B-62-41180 can be used. Alternatively, a glass preform material may be produced from the optical glass of the present invention, and the glass preform material may be pressed to produce an optical element, or an optical glass melted and softened without passing through the glass preform material. A direct press that directly presses to produce an optical element may be used. The optical element is used as various lenses such as biconvex, biconcave, plano-convex, plano-concave, meniscus, mirror, prism, diffraction grating and the like.

The optical glass of the present invention can be obtained in which the wavelength (λ _70% ) exhibiting 70% transmittance at a thickness of 10 mm is 500 nm or less. Due to this light transmittance, a wide range of applications such as compact camera lenses is expected. Furthermore, the preferable range of the wavelength (λ _70% ) is 490 nm or less, and most preferably 480 nm or less.

[Production method]
The optical glass of the present invention is not particularly limited as long as it is a method for producing a normal optical glass. For example, it can be produced by the following method.

  A predetermined amount of each starting material (oxide, carbonate, nitrate, phosphate, sulfate, fluoride salt, etc.) is weighed and mixed uniformly. The mixed raw material is put into a quartz crucible or an alumina crucible, and after rough melting, it is put into a gold crucible, platinum crucible, platinum alloy crucible or iridium crucible and melted at 850 to 1300 ° C. for 1 to 10 hours in a melting furnace. Then, after stirring and homogenizing, the temperature is lowered to an appropriate temperature and cast into a mold or the like to produce glass.

  Next, the manufactured plate-like glass is cut into a predetermined size to form a substantially cubic work piece. This is put into a polishing apparatus and polished to produce a polishing ball. Specifically, the glass is cut into approximately cubes, barrel processing is performed, and the corners of the approximately cubic glass are taken. Thereafter, it is put into an Oscar processing machine and manufactured by performing rough rounding, finishing rounding, and polishing.

  The optical glass of the present invention is typically used for lens, prism and mirror applications. In the production of the optical element of the present invention, a so-called spherical glass preform can be produced by dripping molten glass from the outlet of an outflow pipe of platinum or the like. The polishing ball and the glass preform are produced into an optical element having a desired shape by a precision press molding method.

  Hereinafter, examples of the present invention will be described. However, the following examples are merely for illustrative purposes, and the present invention is not limited to these examples.

<Examples 1-9>
Regarding Examples 1 to 9 of the optical glass according to the present invention, together with the composition, the refractive index (nd), Abbe number (νd), glass transition point (Tg), glass yield point (Ts) and thickness 10 mm of these glasses. Table 1 shows the wavelength (λ _70% ) exhibiting a transmittance of 70% in this glass. The optical glass of the present invention uses the usual optical glass raw materials such as oxides, hydroxides, carbonates, nitrates, fluorides and the like as raw materials for each component, It was weighed and mixed to prepare a raw material for preparation, which was put into a platinum crucible and melted, clarified and stirred at 1000 to 1250 ° C. for 3 to 5 hours according to the meltability depending on the composition and homogenized. Thereafter, it was manufactured by casting into a mold or the like and gradually cooling. In the table, the composition of each component is expressed in mol%.

  Regarding the refractive index and the Abbe number, after maintaining for 2 hours in the vicinity of the glass transition point, the obtained glass was measured based on JOGIS01-2003 with the slow cooling and cooling rate set to -25 ° C / Hr.

  The glass transition point and the glass yield point were measured by the method described in Japan Optical Glass Industry Association Standard JOGIS08-2003 (Measuring Method of Thermal Expansion of Optical Glass) (The temperature rising rate was 8 ° C./min with a thermal expansion measuring device. Measured). However, a sample having a length of 50 mm and a diameter of 4 mm was used as a sample piece.

About the transmittance | permeability measurement, it carried out according to Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the wavelength indicating the transmittance of 70% (λ _70% ) is shown in the glass having a thickness of 10 mm, not the degree of coloring. Specifically, a spectral parallel transmittance of 200 to 800 nm was measured according to JISZ8722 for a facing parallel polished product having a thickness of 10 ± 0.1 mm, and a wavelength (λ _70% ) when the transmittance was _70% was obtained.

As seen in Table 1, all of the optical glasses of Examples (Examples 1 to 10) have optical constants within the specific range, that is, the refractive index (nd) is 1.80 to 2.10, and A glass preform having an Abbe number (νd) of 18 to 40, a glass transition point (Tg) of 680 ° C. or lower, and a glass yield point (Ts) of 720 ° C. or lower, and used for precision press molding. The material was confirmed to be suitable for precision press molding. Further, it was confirmed that the wavelength (λ ₇₀ ) exhibiting a transmittance of 70% in a glass having a thickness of 10 mm is 500 nm or less, and the light transmittance in the visible region is excellent.

Claims (9)

In mole percent on the oxide _basis, B 2 _{O 3} component 25 to 60%, WO ₃ ingredient 1 to 40%, optical glass containing TeO ₂ component from 0.2 to 60%. The optical glass according to claim 1, wherein the content of Nb ₂ O ₅ component is less than 5% in terms of mol% based on oxide. The optical glass according to claim 1, wherein the content of Ga ₂ O ₃ component is less than 1% in terms of mol% based on oxide. In mole percent on the oxide basis, _La 2 _{O 3} ingredient 1 to 35%, and / or optical glass according to any one of claims 1 to 3, the ZnO component contains 1 to 40%. 5. The Bi ₂ O ₃ component is contained in an amount of 0 to 30% in terms of mol% based on the oxide, and the total amount of the TeO ₂ component and the Bi ₂ O ₃ component is 0.2 to 60%. 5. The optical glass described in 1. In mole percent on oxide basis,
Rn ₂ O component (Rn represents one or more selected from the group consisting of Li, Na, K, Cs) 0 to 15%, and / or RO component (R consists of Ba, Sr, Ca, Mg) One or more selected from the group) 0-20%, and / or SiO ₂ component 0-20%, and / or GeO ₂ component 0-20%, and / or P ₂ O ₅ component 0-10%, and / or _Al 2 _{O 3} component 0-20%, and / or _{Gd 2 O 3 + Y 2 O} 3 + Yb 2 O 3 component 0-20%, and / or TiO ₂ component + _Nb 2 O Less than 1% of ₅ components and / or 0-10% of Ta ₂ O ₅ components and / or 0-10% of ZrO ₂ components and / or 0-5 of Sb ₂ O ₃ components + As ₂ O ₃ components %
The optical glass according to claim 1, which is contained.   The optical glass according to any one of claims 1 to 6, wherein the refractive index (nd) is 1.80 to 2.10, and the Abbe number (νd) is 18 to 40.   The optical glass according to any one of claims 1 to 7, which has a glass transition point (Tg) of 680 ° C or lower.   The optical glass according to any one of claims 1 to 8, wherein a wavelength of 70% transmittance in a glass having a thickness of 10 mm is 500 nm or less.