JP2007197258A - Manufacturing method for optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a molded article of optical glass which contains bismuth oxide and has good transmittance. <P>SOLUTION: The method for manufacturing the molded article of optical glass containing Bi<SB>2</SB>O<SB>3</SB>as a component comprises a step of heat-treating a molded optical glass and/or a forming optical glass in an oxidative atmosphere or non-reduction atmosphere. The optical glass comprises a Bi<SB>2</SB>O<SB>3</SB>component in terms of an oxide as the component, so as to improve the transmittance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to an optical glass containing bismuth oxide and a method for manufacturing an optical glass molded article, and an optical glass molded body manufactured by the manufacturing method. More specifically, the present invention relates to a manufacturing method for obtaining a transparent glass molded product by reheating a lens colored by precision press molding, and a processing method for decolorizing an optical glass molded product.

In recent years, integration and high functionality of devices using optical systems have been rapidly advanced, and demands for high accuracy, 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. In addition, since aspherical lenses are often manufactured by precision pressing, 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 addition, aspherical lenses that are difficult to grind and polish can be produced using only a precision press.

Many glasses have been developed as high refractive index and high dispersion region glasses, most of which are phosphate glasses containing Nb ₂ O ₅ with high purity. 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 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. Although these glasses have a relatively low Tg, since the absorption edge of the glass is on the longer wavelength side than 450 nm, the transmittance in the visible region is not sufficient, and as an optical glass that requires high transmittance in the visible region, There was a problem that it could not be used.
JP 2003-321245 A JP-A-8-157231 Japanese Patent Laid-Open No. 2003-300751 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

Further, a glass containing a large amount of bismuth oxide may be colored black by heating in a non-oxidizing atmosphere. In particular, when precision press molding or the like is performed under a non-oxidizing gas such as nitrogen gas, a glass that has been colorless and transparent before molding may turn black after molding, resulting in a phenomenon in which the transmittance is significantly reduced. This phenomenon is not a phenomenon that is confirmed in all Bi ₂ O ₃ glass, but is a phenomenon that is confirmed when certain conditions are met.

The present invention provides a method for producing an optical glass molded article having good transmittance in a glass containing bismuth oxide, an optical element obtained by this production method, and a method for improving the transmittance of the optical glass. Objective.

As a result of intensive studies to solve the above problems, the present inventors have colored Bi ₂ O ₃ -containing glass by precision press molding or the like, because the glass temperature rises when performing precision press molding. As a result, the reactivity between the glass and the surrounding non-oxidizing gas was increased, and it was found that this was caused by the reduction of Bi ₂ O ₃ in the glass. Therefore, it has been found that the coloring can be suppressed or reduced by heat-treating the optical glass molded article in an oxidizing atmosphere or a non-reducing atmosphere after and / or during molding.

That is, the first configuration of the present invention for achieving the above object is a method of manufacturing an optical glass molded article containing a Bi ₂ O ₃ component on the basis of an oxide as a component, which is a molded optical glass. And / or heat-treating the optical glass being molded in an oxidizing atmosphere or a non-reducing atmosphere.

A second configuration of the present invention is the method according to the first configuration, wherein the optical glass contains a B ₂ O ₃ component on an oxide basis as a component.

The third configuration of the present invention is the manufacturing method according to configurations 1 and 2, in which the precision press-molded optical glass or the precision press-molded optical glass is heat-treated in an oxidizing atmosphere or a non-reducing atmosphere.

The 4th structure of this invention is a manufacturing method of the said structures 1-3 whose glass transition temperature of the said optical glass is 530 degrees C or less.

The 5th structure of this invention is a manufacturing method of the said structures 1-4 whose refractive index (nd) of the said optical glass is 1.60 or more, and Abbe number ((nu) d) is 10 or more.

The sixth configuration of the present invention is based on oxide,
Bi ₂ O ₃ : 10% or more and 90% or less B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ : more than 0% and 50% or less RO + Rn ₂ O: more than 0% and 50% or less (where R is Zn, Ba, Sr) , Ca, Mg represents one or more selected from R, and Rn represents one or more selected from Li, Na, K, Cs.)
It is a manufacturing method of the said structures 1-5 containing each component of the composition.

The seventh aspect of the invention, the optical glass, an oxide basis as a constituent component, which is the structure 6 production method of containing Bi ₂ O ₃ 10~70%.
According to an eighth configuration of the present invention, the optical glass is based on an oxide.
Li ₂ O 0-20% and / or Na ₂ O 0-20% and / or K ₂ O 0-20% and / or MgO 0-20% and / or CaO 0-30% and / or SrO 0-40 % And / or BaO 0-40%
According to a ninth configuration of the present invention, which is a manufacturing method of the configuration 7 having the following compositions, the optical glass is based on an oxide,
0 to 20% ZnO and / or _TiO 2 0 to 15% and / or _Nb 2 _O 5 0~15% and / or _WO 3 0 to 15% and / or _Sb 2 _O 3 _0~3%
It is a manufacturing method of the said structure 8 which has each composition of these

A ninth configuration of the present invention is the method according to any one of the above configurations 1 to 8, wherein the heat treatment is performed at a temperature below the yield point of the optical glass.

The 10th structure of this invention is a manufacturing method of the said structures 1-9 whose said non-reducing atmosphere is air | atmosphere or oxidizing gas atmosphere.

Here, when heated in a non-oxidizing atmosphere, the degree of coloring tends to darken as the temperature rises and pale as the temperature decreases, with the yield point (At) as a reference. Heating in an oxidizing atmosphere or in the air is considered effective for decolorizing these.

As described above, the coloring phenomenon of the glass containing Bi ₂ O ₃ is considered to be caused by the change of Bi ^{3+ in} the glass to Bi ⁰ having a color by reduction. The coloring phenomenon due to such a mechanism is reversible, and can be achieved by reducing the color when it is desired to color, or by oxidizing the color when it is desired to fade.

The present invention is characterized in that an optical glass containing a Bi ₂ O ₃ component is heated in an oxidizing atmosphere or a non-reducing atmosphere. Here, in the oxidizing atmosphere or the non-reducing atmosphere, for example, oxygen gas, oxygen halide, oxygen mixed gas (including air) or the like can be used, and heat treatment is performed in oxygen gas or air. It is preferable.

Further, when the glass molded article is precision press-molded, the lens tends to be deformed when the heating temperature is particularly higher than or equal to the yield point, and it is preferable to heat at or below the yield point. Moreover, it is more preferable to heat-process below the temperature of (Tg + At) / 2, and it is the most preferable to heat below the glass transition temperature. Of course, the treatment can be performed by adjusting the atmosphere in the annealing treatment of the press product.

The Bi ₂ O ₃ -containing glass that is the subject of the present invention has a refractive index of 1.60 or more, an Abbe number of 10 to 40, more preferably a refractive index of 1.65 or more, an Abbe number of 15 to 35, most according to needs in optical design. Those having a refractive index of 1.75 or more and an Abbe number of 15 to 30 are preferable. The upper limit of the refractive index is not particularly defined, but 2.3 is preferable as the upper limit.

The Bi ₂ O ₃ -containing glass that is the subject of the present invention has a glass transition temperature (Tg) of 580 ° C. or lower, more preferably 530 ° C. or lower, most preferably 470 ° C. or lower, from the viewpoint of workability in precision press molding. It is.

Next, components contained in the glass of the present invention will be described. In the present specification, unless otherwise specified, all glass compositions are expressed in terms of mass% based on oxides. Here, the “oxide standard” means that the oxide, nitrate, etc. used as a raw material of the glass constituent component of the present invention are all decomposed at the time of melting and changed to an oxide, and the mass of the generated oxide. Is a composition in which each component contained in the glass is described with the total of 100% by mass.

<About essential and optional components>
Bi ₂ O ₃ is a component indispensable for improving the stability of 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 may be deteriorated, and if the amount is too small, it is difficult to satisfy the optical constant that is high in optical design needs. Therefore, the amount of Bi ₂ O ₃ is preferably 10% or more,
More preferably, the lower limit is 15%, most preferably 20%, preferably less than 90%, more preferably 88%, and most preferably 75%.

B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ are components that are very useful as glass forming components, and are components that can improve transmittance, increase viscosity with respect to liquidus temperature, and improve chemical durability. is there. Accordingly, the total content of one or more of these components preferably exceeds 0%, preferably 3% or more, and more preferably 7% or more. However, if the total content of these components is too large, Tg tends to be high, and the upper limit is preferably 50%, more preferably 45%, and most preferably 40%. In addition, by performing the production within this range, a stable glass having a low liquidus temperature can be obtained.

“Liquid phase temperature” means that a glass sample pulverized with a certain particle size is placed on a platinum plate, held in a furnace with a temperature gradient for 30 minutes, then taken out, and the presence or absence of softened glass crystals is observed with a microscope. The lowest temperature at which no crystal is observed.

RO (R = Zn, Ba, Sr, Ca, Mg) is contained in order to improve the melting property of the glass and adjust to an arbitrary optical constant. Rn ₂ O (Rn = Li, Na, K, Cs) is contained in order to improve the melting property of the glass and to lower the Tg. However, even if the Rn ₂ O component is free, the target Tg = 530 ° C. or less can be satisfied. Therefore, in view of improving chemical durability, the Rn ₂ O component can be free. The total content of these RO and Rn ₂ O components is preferably more than 0%, more preferably more than 1%, most preferably 3% or more. Also, if the total content of the RO and Rn ₂ O components is too large, the liquid phase temperature may increase or the chemical durability may decrease, so the total content is preferably 50%, more preferably The upper limit is 45%, most preferably 40%.

Li ₂ O is a component effective for lowering Tg, improving glass stability and meltability, but if its amount is too large, chemical durability tends to decrease. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 5%.

Na ₂ O is a component having an effect of lowering Tg and improving meltability. However, if its amount is too large, glass stability and chemical durability are likely to be lowered. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 5%.

K ₂ O is a component having an effect of lowering Tg, but if the amount is too large, the glass stability is lowered and the chemical durability is likely to be lowered. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 5%.

MgO is a component having an effect of greatly increasing the dispersion, but if its amount is too large, devitrification resistance may be lowered in the press temperature range. Therefore, the upper limit is preferably 20%, more preferably 10%, and most preferably 5%.

CaO 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%.

SrO 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%.

BaO is a component that increases the refractive index of glass and has an effect on 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%.

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

TiO ₂ is an effective component for adjusting the optical constant to a high refractive index and high dispersion, but 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%.

Nb ₂ O ₅ is a component that is effective in increasing the refractive index of glass, but if the amount is too large, glass stability is easily lowered. Therefore, the upper limit is preferably 15%, more preferably 10%, and most preferably 5%.

WO ₃ is a component having an effect of highly dispersing 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%.

Sb ₂ O ₃ is a component having an effect of defoaming agent, glass redox control, and high dispersion. However, when the amount is too large, meltability is deteriorated and transmittance is easily lowered. Therefore, the upper limit is preferably 3%, more preferably 2%, and most preferably 1%.

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.

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 Pb, 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 reached. Until then, environmental measures 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 is a component that is used to improve bubble breakage (destroyability) when melting glass. However, when glass is manufactured, processed, and disposed of, measures for environmental measures are taken. Since it is necessary to take, it is not preferable to contain As ₂ O ₃ in the glass of the present invention.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to the following. The glass composition, optical constant, and Tg point which performed the detachable color process in the Example of this invention are shown. As described above, both are optical glasses having a low Tg and a high refractive index and high dispersion. As the glass to which the heat treatment method of the present invention can be applied, glass containing a predetermined amount of Bi ₂ O ₃ is preferable as described above, and examples thereof are shown in Tables 1 and 2.

In Table 1, after preparing and mixing the glass shown in Example 1 using ordinary glass raw materials, a fused glass was produced at 900 ° C. × 1 hour using a quartz crucible, and transferred to a platinum crucible. It was prepared by casting after defoaming and stirring at 2 ° C. for 2 hours. Further, for slow cooling, the temperature was maintained at 450 ° C. for 2 hours, and the temperature was decreased to 200 ° C. over 8 hours. In addition, said melting condition is an example and it can change to appropriate conditions by seeing the state of glass.

The glass immediately after slow cooling (hereinafter referred to as the original material) was pale yellow. This glass was cut into 1 cm cubic shapes with a cutting machine, and the surface was further polished and heat-treated under nitrogen gas. The reason why the nitrogen gas treatment is performed here is to reproduce a precision press that is generally performed by heating under nitrogen gas.

The heat treatment at this time is carried out in a precision press without molding, and the temperature is raised to 482 ° C. of the yield point (At): 8.8 K / sec, holding time: 300 sec, temperature drop: 2.24 K / sec Carried out. Coloring gradually progressed inward from the glass surface. Further, as the heat treatment temperature increased or the treatment time increased, the coloration of the glass tended to become intense.

In FIG. 1, the transmission spectrum before heat processing of the glass of Example 1 and the transmission spectrum after processing on the above-mentioned conditions are shown. It can be confirmed that the transmittance at 450 nm is deteriorated by about 10% by heat treatment from the transmission spectrum of the base material as shown in FIG. 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 color fading operation of the glass colored in Example 1 was performed by using an annealing furnace in the air at a glass transition point (Tg) of 442 ° C. over 1 hour, held for 2 hours, and then over 200 hours over 8 hours The temperature was lowered. Further, fading of the glass can be promoted as the heat treatment temperature rises or the treatment time becomes longer.

FIG. 2 shows changes in the transmission spectrum due to the heat treatment. It can be seen that the transmission spectrum has returned to the same level as the original material by heat treatment in the atmosphere. Examples other than Example 1 can also perform a coloring operation and a fading operation by the above processing.

It is also possible to partially heat by applying the above-mentioned treatment and to partially color by blowing a non-oxidizing gas, and naturally it is possible to cause a difference in transmittance in the glass bulk.

Transmission spectrum of glass of Example 1 before heat treatment and transmission spectrum after treatment under the above-mentioned conditions Change of transmission spectrum by heat treatment

Claims (11)

A method for producing an optical glass molded article containing a Bi ₂ O ₃ component on the basis of an oxide as a constituent component, wherein the molded optical glass and / or the optical glass being molded is subjected to an oxidizing atmosphere or non-reducing property. The manufacturing method characterized by including the process heat-processed in atmosphere. The method according to claim 1, wherein the optical glass contains a B ₂ O ₃ component on an oxide basis as a constituent component. 3. The method according to claim 1, wherein the optical glass that has been precision press-molded or the optical glass that is being precision press-molded is heat-treated in an oxidizing atmosphere or a non-reducing atmosphere. The glass transition temperature of the said optical glass is 530 degrees C or less, The manufacturing method in any one of Claims 1-3. The manufacturing method according to claim 1, wherein the optical glass has a refractive index (nd) of 1.60 or more and an Abbe number (νd) of 10 or more. On oxide basis,
Bi ₂ O ₃ : 10% or more and 90% or less B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ : more than 0% and 50% or less RO + Rn ₂ O: more than 0% and 50% or less (where R is Zn, Ba, Sr) , Ca, Mg represents one or more selected from R, and Rn represents one or more selected from Li, Na, K, Cs.)
The manufacturing method in any one of Claims 1-5 containing each component of the composition of these. Wherein the optical glass, an oxide basis as a component, the manufacturing method according to claim 1, a _Bi 2 _{O 3,} characterized in that it contains 10% to 70%. The optical glass is based on oxide as a constituent component,
Li ₂ O 0-20% and / or Na ₂ O 0-20% and / or K ₂ O 0-20% and / or MgO 0-20% and / or CaO 0-30% and / or SrO 0-40 % And / or BaO 0-40%
The manufacturing method of Claim 7 which has each composition of these The optical glass is based on oxide as a constituent component,
0 to 20% ZnO and / or _TiO 2 0 to 15% and / or _Nb 2 _O 5 0~15% and / or _WO 3 0 to 15% and / or _Sb 2 _O 3 _0~3%
The manufacturing method of the said structure 8 which has each composition of these. The method according to claim 1, wherein the heat treatment is performed at a temperature below the yield point of the optical glass. The manufacturing method according to claim 1, wherein the non-reducing atmosphere is air or an oxidizing gas atmosphere.

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