JP2008184355A - Optical glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass having excellent permeability, relating in particular to a glass containing bismuth oxide. <P>SOLUTION: The permeability of a glass can be increased by oxidization effect by stirring and oxidation effect by an oxidative gas while a raw material mixture of the optical glass containing Bi<SB>2</SB>O<SB>3</SB>is set to be incorporated with a raw material which thermally decomposes to an oxidative gas and/or a raw material which can emit another gas. A method of producing an optical glass is performed by melt-molding a raw material mixture containing at least 10% of Bi<SB>2</SB>O<SB>3</SB>component by mass% based on the oxide. In the method, the raw material mixture contains a component, at least 3% of the total mass, which does not remain as a constituent component of a glass. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an optical glass containing bismuth oxide, and more particularly to an optical glass containing bismuth oxide capable of improving the transmittance.

In recent years, rapid progress has been made in integration and high functionality of devices that use optical systems, and demands for high precision, light weight, and miniaturization of optical systems are increasing. Along with this, in order to reduce the number of lenses, optical design using aspherical lenses of high refractive index and high dispersion glass is becoming mainstream. Since aspherical lenses are often manufactured by precision pressing, a low Tg optical glass that can be manufactured at low cost is desired. The advantage of precision press molding is that the lens can be molded to the final shape without grinding and polishing. In particular, an aspheric lens that is difficult to grind and polish can be produced only by a precision press.

Many glasses have been developed as high refractive index and high dispersion region glasses, most of which are phosphate glasses containing a large amount of Nb ₂ O ₅ component. For example _P 2 _O 5 _-Nb 2 _O 5 in Patent Documents _{1,2 -WO 3 - (K 2 O} , Na 2 O, Li 2 O) based on glass Patent Document 3 _{P 2 O} 5 -Nb 2 An O ₅ —TiO ₂ —Bi ₂ O ₃ —Na ₂ O-based glass is disclosed. However, these optical glasses have disadvantages that the glass transition point (Tg) is not so low and the devitrification resistance is insufficient.

Further, as a glass having a low glass transition point (Tg), a glass containing a large amount of Bi ₂ O ₃ component has been developed. For example, Non-Patent Documents 1 to 5 include Bi ₂ O ₃ —Ga ₂ O ₃ —PbO system, Bi ₂ O ₃ —Ga ₂ O ₃ — (Li ₂ O, K ₂ O, Cs ₂ O) system, Bi _{A 2} O ₃ —GeO ₂ system is disclosed. These glasses have the advantage that the Tg can be relatively low while maintaining a high refractive index, but because the absorption edge of the glass is on the longer wavelength side than 450 nm, the transmittance in the visible region is not sufficient, There is a problem that it cannot be used as an optical glass that requires high transparency in the visible region.

Various attempts have been made to improve the transmittance in the visible region in the glass containing a large amount of the Bi ₂ O ₃ component.

Patent Document 4 describes that one of the causes is that the deterioration of the transmittance is caused by the reduction of a large amount of Bi ₂ O ₃ contained in the glass composition. Therefore, in order to suppress the disadvantages due to these reducing actions, it is possible to achieve a certain effect by improving production technology, for example, increasing the oxygen concentration in the molten atmosphere or bubbling oxygen into the molten glass. It describes what you can do.

  However, these production technical improvements have disadvantages such as not only a large cost for adding oxygen gas bubbling and flow equipment, but also a large cost for the oxygen gas used. Particularly for oxygen bubbling, oxygen is blown into the glass, so that a large number of bubbles are generated, and the transmittance due to the bubbles may be reduced, which may not always be appropriate for optical glass.

Therefore, optical glass containing a large amount of the Bi ₂ O ₃ component is not reduced by glass (bismuth oxide) even if it is melted at an atmospheric oxygen concentration without requiring the addition of a large-scale apparatus. There has been a demand for a method capable of producing optical glass with good light transmittance.
JP 2003-321245 A JP-A-8-157231 Japanese Patent Laid-Open No. 2003-300751 JP 2005-502574 A Physics and Chemistry of Glasses, P119, Vol. 27 No. 3 June 1986 American Ceramic Society, P.M. 2315, Vol. 75, no. 9, October 1992 American Ceramic Society, P.M. 10, 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

The present invention has been made in view of the problems as described above, and provides an optical glass containing bismuth oxide that does not cause deterioration in transmittance due to reduction of bismuth oxide and an optical glass manufactured by the manufacturing method. .

A first configuration of the present invention is a method for producing an optical glass by melt-molding a raw material mixture containing 10% or more of a Bi ₂ O ₃ component by mass% based on an oxide, and in the raw material mixture, It is the said manufacturing method characterized by containing the component which 3% or more of mass does not remain as a glass structural component.

The method described in the constitution 1 is an effective method for producing optical glass containing a large amount of Bi ₂ O ₃ component, specifically, optical glass containing 10% by mass or more of Bi ₂ O ₃ component. .
Here, “3% or more of the total mass does not remain as a glass component” means that a part of a powder material such as an oxide used as a glass material is usually melted at high heat. A gas component that reacts with oxygen or the like in the air and does not remain as a final glass component. For example, CO ₂ generated from a metal carbonate corresponds to this.

  By using such a raw material, a large amount of gas is released from the raw material mixture in the normal glass melting process, and the release of the gas makes it easier to produce a stirring effect in the molten glass. It can be expected that the oxidation will proceed and the transmittance will be improved by contact.

According to a second configuration of the present invention, the raw material mixture includes a component that is thermally decomposed when glass is melted and released as a molecule composed of oxygen and / or oxygen and other elements. It is a manufacturing method.

According to this aspect, since the gas released from the raw material mixture is a molecule containing oxygen, the oxidation effect is usually greater than that of a gas such as fluorine or chlorine, and the transmittance can be further improved.

According to a third configuration of the present invention, the component that does not remain in the raw material mixture is one that is thermally decomposed when glass is melted and released as a gas containing a nonmetallic component. It is a manufacturing method.

According to this aspect, since a gas containing a nonmetallic element is released from the raw material mixture, a stirring effect is likely to occur in the molten glass. Therefore, it becomes easy for the molten glass and oxygen in the atmosphere to come into contact with each other, and the glass is gradually oxidized, which tends to improve the transmittance. Here, the gas containing a non-metallic component is generated by a raw material such as a metal or silicon peroxide, carbonate, sulfate, or hydrate.

A fourth configuration of the present invention is the manufacturing method according to claim 2 or 3, wherein the substance released from the raw material by the thermal decomposition is an oxidizing gas.

According to this aspect, the oxidizing gas generated when the raw material is melted prevents Bi ₂ O ₃ from being reduced, and as a result, coloring of the optical glass can be prevented.

The 5th structure of this invention is a manufacturing method of the said structures 1-5 which makes oxygen concentration in a vitrification process and / or clarification process atmosphere 1% or more.

According to this aspect, since the lower limit of oxygen during the vitrification step and / or the refining step is 1%, an oxidation reaction easily occurs and the transmittance of the glass is easily improved.

A sixth configuration of the present invention is an optical glass manufactured by the method of the above configurations 1 to 5, and an optical constant having a refractive index [nd] of 1.70 or more and an Abbe number [νd] of 10 or more. The optical glass.

Since the glass of this embodiment is a glass having a high refractive index and high dispersion, the number of lenses can be reduced, and the equipment using the optical system can be reduced in weight and size.

The seventh configuration of the present invention is the optical glass of the above configuration 6 having a glass transition point of 530 ° C. or lower.

According to this aspect, since the glass transition point is 530 ° C. or lower, the temperature during press molding can be set to about 600 ° C. or lower. Therefore, the temperature at the time of reheating can be set low, and the life of the precision press-molding die can be extended.

The 8th structure of this invention is the optical glass of the said structures 6 and 7 containing RO component (R is 1 or more types selected from the group which consists of Zn, Ba, Sr, Ca, Mg).

According to this aspect, glass stability can be improved by containing an alkaline earth metal oxide and ZnO.

A ninth configuration of the present invention is the optical glass according to any of the above configurations 6 to 8, wherein the optical glass contains one or more of B ₂ O ₃ , SiO _2, and Al ₂ O ₃ components.

According to this embodiment, the stability of the glass containing a large amount of Bi component can be improved.

Tenth aspect of the present invention, _B 2 _O 3 0~30% as an optional component in weight percent on the oxide basis and / or _SiO 2 0 to 30% and / or Al ₂ O ₃ 0 to 20% and / or TiO ₂ 0-20% and / or Nb ₂ O ₅ 0-20% and / or WO ₃ 0-15% and / or Ta ₂ O ₅ 0-15% and / or ZrO ₂ 0-15% and / or ZnO 0-20% and / or 0-20% MgO and / or CaO 0 to 30% and / or SrO 0 to 40% and / or BaO 0 to 40% and / or Li ₂ O 0-20% and / or Na ₂ O 0-20% and / or K ₂ O 0-20% and / or Cs ₂ O 0-20% and / or Rn ₂ O component (Rn = selected from the group consisting of Li, Na, K, Cs 1 or more) is 30% or less Y ₂ O ₃ 0-10% and / or La ₂ O ₃ 0-10% and / or Gd ₂ O ₃ 0-10% and / or Yb ₂ O ₃ 0-10% and / or P ₂ O ₅ 0-10% And / or Sb ₂ O ₃ 0-3% and / or GeO ₂ 0-20%
And the total amount of F in which a part or all of the oxide is substituted with fluoride is in the range of 0 to 5% by mass with respect to 100% by mass of the oxide reference composition. And RO (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca and Mg) + Rn ₂ O (Rn is one or more selected from the group consisting of Li, Na, K and Cs) ) Is 50% or less, and Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ is 10% or less.

By producing an optical glass with the above composition, it has a desired refractive index and Abbe number, has a sufficiently low glass transition point, excellent defoaming properties, and easily obtains the desired optical glass at a low production cost.

The eleventh configuration of the present invention is a precision press-molding preform made of the optical glass having the above-described configurations 6 to 10.

The twelfth configuration of the present invention is an optical element formed by precision press-molding the preform having the above-described configuration 11.

The optical glass of the present invention can avoid transmittance deterioration due to reduction by adopting the above-described constituent requirements, and can obtain an optical glass with good light transmittance. In addition, according to the production method of the present invention, it is possible to obtain a glass having a high refractive index, a high dispersibility, and a low glass transition point while improving coloring by reduction in an optical glass mainly composed of Bi ₂ O _3. it can. For example, even when the produced glass has poor light transmission due to coloring due to reduction and cannot be used for optical purposes, only the transmittance is obtained without substantially changing the composition component of the glass obtained according to the present invention. It is possible to improve.

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 mass of oxides is 100% by mass, and each component contained in the glass is expressed. The total amount of F in which a part or all of the above 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 achieving high refractive index, high dispersion, low Tg, and improved chemical durability. However, if the amount is too large, the transmittance of the glass itself before pressing tends to be deteriorated, and if it is too small, it is difficult to satisfy optical constants that are high in optical design needs. Accordingly, the Bi ₂ O ₃ component amount is preferably 10%, more preferably 15%, most preferably 20% as the lower limit, preferably less than 90%, more preferably 88%, and most preferably 85%. . In the present invention, when using BiONO ₃ as raw materials for supplying the Bi ₂ O ₃ component, to be particularly effective in the transmittance decreases prevention have been confirmed.

The RO component (one or more selected from the group consisting of R = Zn, Ba, Sr, Ca, Mg) can be contained in order to improve the meltability of the glass and adjust to an arbitrary optical constant. If it is contained excessively, the stability, the chemical durability, and the transmittance tend to decrease. Accordingly, the total content of RO components is preferably more than 0%, more preferably 0.5%, most preferably 1% as a lower limit, preferably 40%, more preferably 20%, most preferably 10%. % Is the upper limit.

The ZnO component is a component that is effective in improving chemical durability and transmittance, but if the amount is too large, the glass stability is easily lowered. Therefore, the upper limit is preferably 20%, more preferably 15%, and most preferably 10%.

The MgO component is a component having an effect of greatly increasing 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 20%, more preferably 10%, and most preferably 5%.

The CaO component is a component having an effect of improving the transmittance and improving the glass stability, but if the amount is too large, the glass stability tends to be lowered. Therefore, the upper limit is preferably 30%, more preferably 20%, and most preferably 15%.

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 transmittance is easily lowered. Therefore, the upper limit is preferably 40%, more preferably 15%, and most preferably 10%.

The BaO component increases the refractive index of the glass and is an effective component for glass stability. 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 40%, more preferably 15%, and most preferably 10%.

An Rn ₂ O component (one or more selected from the group consisting of Rn = Li, Na, K, and Cs) is an optional component that can reduce the glass transition point and improve glass stability by containing an appropriate amount. It is. However, when it is contained excessively, it tends to cause a decrease in chemical durability and a deterioration in devitrification resistance. Accordingly, the total content of the Rn ₂ O component is preferably more than 0%, more preferably 0.5%, most preferably 1% as the lower limit, preferably 30%, more preferably 20%, most preferably The upper limit is 10%. However, it does not matter if it is not contained.

The Li ₂ O component is a component effective for lowering Tg, improving glass stability, and melting property. However, if the amount is too large, crystallization of the quartz crucible is promoted and its durability may be reduced. There is a disadvantage from the viewpoint of production technology. Therefore, the upper limit is preferably 20%, more preferably 15%, and most preferably 10%.

Na ₂ O is a component that is effective in reducing Tg and improving meltability, but if the amount is too large, the stability of the glass tends to decrease. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 5%.

The K ₂ O component is a component that lowers the glass transition point and is effective in improving the meltability. However, if the amount is too large, the chemical durability is lowered and the stability of the glass tends to be lowered. Therefore, the upper limit is preferably 20%, 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 20%, more preferably 10%, and most preferably 5%.

Furthermore, when placing importance on glass stability, the upper limit of the total amount of the RO and Rn ₂ O components is preferably 50% or less, more preferably 45% or less, and most preferably 40%, from the viewpoint of glass stability. % Or less.

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. . Accordingly, the total content of one or more of these components preferably exceeds 0%, more preferably 3% or more, and most preferably 7% or more. However, if the total content of these components is too large, the glass transition point (Tg) tends to be high, and therefore the upper limit is preferably 50%, more preferably 45%, and most preferably 40%. By producing in this range, a stable glass having a low liquidus temperature can be obtained.

The B ₂ O ₃ component is not an essential component, but it is a useful component for improving the glass stability. However, if the amount is too large, the stability of the glass deteriorates and the thermal properties (glass transition point, etc.) ) Tends to be high. Therefore, it is preferable to contain more than 0%, more preferably 0.1%, most preferably 0.2% is the lower limit, preferably 30%, more preferably 20%, most preferably 10% is the upper limit. And

Although the SiO ₂ component is not an essential component, it is a useful component for improving the glass stability and increasing the viscosity of the glass. However, if the amount is too large, the glass stability tends to deteriorate. Therefore, it is preferable to contain more than 0%, preferably 0.1%, more preferably 0.2% as the lower limit, preferably 30%, more preferably 20%, most preferably 10%. The upper limit.

The Al ₂ O ₃ component is not an essential component, but it is a useful component for improving the glass stability and improving the chemical durability and mechanical strength. It becomes easy to get worse. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 7%.

The TiO ₂ component is an optional component effective for adjusting the optical constant to a high refractive index and high dispersion. However, if the amount is too large, the transmittance is lowered and the glass stability tends to deteriorate. Therefore, the upper limit is preferably 20%, more preferably 15%, and most preferably 10%.

The Nb ₂ O ₅ component is an optional component effective for increasing the refractive index of the glass, but if the amount is too large, the glass stability tends to deteriorate. Therefore, the upper limit is preferably 20%, more preferably 15%, and most preferably 10%.

The WO ₃ component is an optional component that has an effect of highly dispersing the glass. However, if the amount is too large, the glass stability tends to be lowered, and the transmittance tends to deteriorate. 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 as a high refractive index increasing component, but if the amount is too large, the stability of the glass tends to deteriorate. 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 tends to deteriorate. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

The components Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , and Yb ₂ O ₃ are optional components that are effective in improving the chemical durability of the glass, but dispersion is desired when the amount is large. It tends to be lower than the value and the devitrification resistance tends to increase. Therefore, the upper limit of each of the above components is preferably 10%, preferably 7%, and most preferably 5%. In addition, there is no problem if each component is 10% or less, but when devitrification resistance is further emphasized, the upper limit of the total amount of this component is also preferably 10%, and preferably 7%. Preferably, 5% is most preferable.

The P ₂ O ₅ component is an optional component effective for improving glass stability. However, when the amount is too large, the tendency of phase separation of the glass tends to become strong. Therefore, the upper limit value is preferably 10%, more preferably 5%, and most preferably 1%. This does not include cases where emphasis is placed on phase separation prevention.

The Sb ₂ O ₃ component is an optional component having an effect of defoaming agent, glass redox control and high dispersion. If the amount is too large, the meltability is deteriorated and the transmittance is easily lowered. 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 20%, more preferably 10%. More preferably, it is made into%. Most preferably not.

F has the effect of increasing the meltability of the glass and can be added arbitrarily, but the refractive index may be drastically lowered. Therefore, when the total amount of F in which a part or all of the oxide is fluoride-substituted is expressed in mass% when calculated as F atoms based on 100 mass% of the oxide standard composition, the upper limit The value is preferably 5%, more preferably 3%, still more preferably 1%. Most preferably not.

In the present invention, it is required that a part of the raw material is decomposed, volatilized or the like and does not remain in the final glass when it is melted. For that purpose, it is preferable to use raw materials other than oxides as raw materials. For example, chloride, peroxide, nitrate, carbonate and the like can be mentioned.

Moreover, it is preferable that the quantity of the component which does not remain in glass finally as a raw material is 3 to 40% with respect to the total mass of a raw material. If it is too much, the reactivity becomes high at the time of melting, and disadvantages such as overflowing of the molten glass from the crucible may occur. The transmittance cannot be improved. Therefore, the content of the component not finally remaining in the glass as the raw material is preferably 3%, more preferably 5%, and most preferably 7% of the total mass of the raw material, preferably 40%, more preferably The upper limit is preferably 30%, and most preferably 20%.

As long as the gas generated by decomposition is not a gas that reduces glass, the gas can be brought into contact with oxygen in the atmosphere due to the stirring effect, so that an improvement in transmittance due to its oxidizing action can be expected. Therefore, carbon dioxide gas, chlorine gas, sulfuric acid gas, nitric acid gas, etc. can be used. However, it is more preferable if it is a gas having an oxidizing action, and the most preferable gas is an oxygen-containing gas.

If the atmosphere at the time of melting is not a reducing atmosphere, oxidation is promoted by the oxidizing gas released from the molten glass, and the transmittance tends to be improved. Preferably, it melts in an atmosphere having an oxygen concentration of 1% or more, more preferably 2% or more, and most preferably 3% or more.

As the melting temperature, the melting of the molten glass is easily promoted by melting at the lowest possible temperature. Therefore, it is preferable to melt at as low a temperature as possible without causing trouble in vitrification and clarification.

<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. It tends to cause 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 tends to increase, 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 blowout of foam (destructive property) when melting glass, but measures for environmental measures when manufacturing, processing, and disposing of glass. Therefore, it is not preferable to contain 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 5-50%,
SiO ₂ 0-30% or less,
B ₂ O ₃ 0-50% 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 0-1% and / or
GeO ₂ 0-20% and / or
TeO ₂ 0-5% and / or F 0-10% and / or

The optical glass of the present invention has a high refractive index and a high dispersion, and can easily obtain a glass transition point (Tg) of 530 ° C. or lower. In consideration of the above, a more preferable range of Tg is 510 ° C. or less, and further preferably 480 ° C. or less. If this range is exceeded, the mold film and mold material that can be used are greatly limited.

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.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to the following. The compositions of Example 1 and Comparative Example 1 differ only in the supply form of the raw materials for supplying some components. Although the oxide raw material is used for Comparative Example 1, Example 1 is characterized by containing carbonate, hydroxide, and nitrate. In addition, the component ratio of each component in a table | surface is converted into an oxide reference | standard, and raw material content is (for each component of each raw material for making each composition represented by an oxide reference | standard contain in glass) Relative weight (on oxide basis). “Vitrification ratio” refers to a numerical value represented by “glass weight / raw material mixture weight”, and the smaller this value is, the greater the ratio of being volatilized and not remaining in the glass.

The raw materials were weighed so as to have a glass weight of 600 g in the composition and raw material forms shown in Table 1, and mixed uniformly. After coarse dissolution at 650 ° C. to 900 for 2 to 3 hours using a quartz crucible, the temperature was adjusted to about 800 ° 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 optical glass of the example was measured for refractive index [nd]], Abbe number [νd], and transmittance. The transmittance was determined in accordance with Japan Optical Glass Industry Association Standard JOGIS02. Specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm is measured in accordance with JISZ8722 to measure a spectral transmittance of 200 to 800 nm.

The refractive index [nd] and the Abbe number [νd] were measured for the obtained glass with a slow cooling drop temperature of −25 ° C./hr.

In FIG. 1, the transmission spectrum of the glass of Example 1 and Comparative Example 1 is shown. The composition of Example 1 was obtained by substituting BiONO _{3 for} a part of Bi ₂ O ₃ in the composition of Comparative Example 1, and the transmittance was drastically improved by such composition replacement. As described above, by changing the raw material form of a part of the raw material, the transmittance, which is a specific problem of the Bi component-containing glass, can be greatly improved without incurring a great production technical cost.

It is a curve which shows the transmittance | permeability of the optical glass of this invention, and a comparative example.

Claims (12)

A method of producing an optical glass by melt-molding a raw material mixture containing 10% or more of a Bi ₂ O ₃ component by mass% based on an oxide, wherein 3% or more of the total mass is a glass component in the raw material mixture The said manufacturing method characterized by including the component which does not remain as. The manufacturing method according to claim 1, wherein the raw material mixture includes a material that is thermally decomposed when glass is melted and released as molecules composed of oxygen and / or oxygen and other elements. 3. The method according to claim 1, wherein the component not remaining in the raw material mixture is thermally decomposed when the glass is melted and released as a gas containing a nonmetallic component. The method according to claim 2 or 3, wherein the substance released from the raw material by the thermal decomposition is an oxidizing gas. The manufacturing method according to any one of claims 1 to 4, wherein the oxygen concentration in the atmosphere in the vitrification step and / or the refining step is 1% or more. 6. The optical glass produced by the method according to claim 1, wherein the optical glass has an optical constant having a refractive index [nd] of 1.70 or more and an Abbe number [νd] of 10 or more. The optical glass according to claim 6, which has a glass transition point of 530 ° C. or lower. The optical glass according to claim 6 or 7, comprising an RO component (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca, and Mg). The optical glass according to claim 6, comprising at least one of B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ components. _B 2 _O 3 0 to 30% as an optional component in weight percent on the oxide basis and / or _SiO 2 0 to 30% and / or Al ₂ O ₃ 0 to 20% and / or TiO ₂ 0 to 20% and / or Nb ₂ O ₅ 0-20% and / or WO ₃ 0-15% and / or Ta ₂ O ₅ 0-15% and / or ZrO ₂ 0-15% and / or ZnO 0-20% and / or MgO 0 20% and / or CaO 0 to 30% and / or SrO 0 to 40% and / or BaO 0 to 40% and / or Li ₂ O 0 to 20% and / or Na ₂ O 0 to 20% and / or The total of K ₂ O 0-20% and / or Cs ₂ O 0-20% and / or Rn ₂ O component (one or more selected from the group consisting of Rn = Li, Na, K, Cs) is 30 % Y ₂ O ₃ 0-10% and / or The La ₂ O ₃ 0~10% and / or Gd ₂ O ₃ 0~10% and / or Yb ₂ O ₃ 0~10% and / or P ₂ O ₅ 0~10% and / or Sb ₂ O ₃ 0 3% and / or GeO ₂ 0 to 20%
And the total amount of F in which a part or all of the oxide is substituted with fluoride is in the range of 0 to 5% by mass with respect to 100% by mass of the oxide reference composition. And RO (R is one or more selected from the group consisting of Zn, Ba, Sr, Ca and Mg) + Rn ₂ O (Rn is one or more selected from the group consisting of Li, Na, K and Cs) ) Is 50% or less, and Y ₂ O ₃ + La ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ is 10% or less, The optical glass according to claim 6, . A precision press-molding preform comprising the optical glass according to claim 6. An optical element formed by precision press-molding the preform according to claim 11.

Images