WO2010095611A1

WO2010095611A1 - Optical glass

Info

Publication number: WO2010095611A1
Application number: PCT/JP2010/052261
Authority: WO
Inventors: 淳一中村; 達雄日高; 拓朗池田; 英和橋間; 直之北村; 幸平福味; 準治西井
Original assignee: 日本山村硝子株式会社; 独立行政法人産業技術総合研究所
Priority date: 2009-02-17
Filing date: 2010-02-16
Publication date: 2010-08-26
Also published as: JPWO2010095611A1

Abstract

Disclosed is an optical glass that has a high refractive index and high transmittivity, as well as being suitable for forming general lenses and aspherical lenses, and that additionally is suitable for forming lenses and other optical elements with light wave controlling functions that have a nano-order level microstructure produced by molding with a precision molding press. The optical glass contains, as oxide equivalents of phosphorus, bismuth, and zinc, P₂O₅: 15‑30 mol%, Bi₂O₃: 5‑35 mol%, and ZnO: 40‑75 mol%, contains, as oxide equivalent of antimony, Sb₂O₃: 0.05‑0.50 mol%, and contains no fluorine F. Furthermore, the glass may also contain, as the total amount of one, two, or more alkaline metal elements R, as oxide equivalent, R₂O: 2‑15 mol%, as required.

Description

Optical glass

The present invention relates to an optical glass, and more particularly to an optical glass having a high refractive index, a high transmittance, and a material characteristic of a low yield point, which is suitable for molding an optical lens by precision molding or the like.

In recent years, aspherical lenses are increasingly used as optical devices are remarkably reduced in size and weight. This is because aspherical lenses can easily correct light aberration, reduce the number of lenses, and make the device compact.
In addition, there is an increasing demand for an optical element that exhibits a light wave control function, that is, a light wave control element, by forming a nano-fine structure having a light wavelength level period on the glass surface. With the light wave control function, structural birefringence, prevention of surface reflection, and the like can be obtained. Moreover, a wide application range can be expected by manufacturing such a light wave control element with glass.
An aspherical lens or the like is manufactured by heat-softening a glass preform and precision molding it into a desired shape.
As for the production of the light wave control element, research and development of a glass imprint by a precision molding method using a heat-resistant mold in which a nano-fine structure having a period of 100 nm to 10 μm is formed has been made from the viewpoint of low cost.
In order to obtain a glass molded product by precision molding, it is necessary to perform pressure molding of the preform at a temperature in the vicinity of the yield point (At). For this reason, the higher the yield point (At) of the preform, the more the mold (mold) in contact with it is exposed to a higher temperature, the mold surface is oxidized and consumed, and the mold maintenance is required. Mass production cannot be realized. For this reason, it is desired that the optical glass constituting the preform can be molded at a relatively low temperature, and therefore has a low yield point (At).
As a glass system having a low yield point (At), a phosphate optical glass mainly composed of phosphate can be raised.

On the other hand, as glass used for optical members including mold lenses, those having various optical properties are required depending on the application, and in particular, there is an increasing demand for those having high refractive index and high transmittance. ing.

As a conventional glass that satisfies the requirements for the above optical properties, for example, P ₂ O ₅ —B ₂ O ₃ —R ₂ O—WO ₃ —Nb ₂ O ₅ —TiO ₂ glass disclosed in Patent Document 1 And P ₂ O ₅ —B ₂ O ₃ —R ₂ O—R′O—WO ₃ —Nb ₂ O ₅ —Bi ₂ O ₃ glass disclosed in Patent Document 2. However, R is an alkali metal element and R ′ is an alkaline earth metal element.
Some of these glasses have a refractive index (n _d ) of 1.75 to 2.0.
Patent Document 3 discloses a high-refractive index, high-dispersion optical glass for precision press molding of P ₂ O ₅ —Nb ₂ O ₅ —Bi ₂ O ₃ glass.

By the way, the present inventors are energetically conducting research on phosphate-based optical glasses mainly composed of phosphate, particularly zinc bismuth phosphate-based glasses. ing.
Patent applications are also filed according to Patent Document 4 and Patent Document 5. Patent Document 4 is an optical glass for glass imprinting, has a low yield point in the range of 340 ° C. to 450 ° C., has a good transmittance at 400 nm, has no color appearance, and causes surface discoloration during molding using a mold. There is no, and moldability is good. Further, the optical glass described in Patent Document 5 is obtained by adding fluorine F to the glass composition described in Comparative Examples 1 to 4 of Patent Document 4, that is, a glass composition having a high refractive index (n _d ) exceeding 1.82. As a result, it was found out that there is an effect in improving the transmittance and lowering the yield point (At), and was completed.

JP 2002-173336 A JP 2006-131480 A JP 2001-58845 A JP 2009-184900 A JP 2009-256170 A

However, the optical glass disclosed in Patent Document 1 and Patent Document 2 described above has a yield point (At) as high as 492 ° C. or higher in Patent Document 1 and 526 ° C. or higher in Patent Document 2, and the life of the mold is increased. There were many cases that could not be expected.
Further, in the optical glass of Patent Document 3 which can be expected to have a lower yield point and a higher refractive index, absorption of light on the short wavelength side due to Bi ₂ O ₃ is large, light transmittance at a wavelength of 400 nm is low, and appearance Many of them were quite yellow. That is, in the optical glass disclosed in Patent Document 3, the light transmittance at 400 nm is 55%, which is less than 70%, and there is a problem that the applicable range as an optical member becomes narrow.
The glass imprint optical glass described in Patent Document 4, refractive index (n _d) it is difficult 1.77 or more high refractive index. Furthermore, since the optical glass described in Patent Document 5 contains fluorine F, a toxic fluorine component is easily volatilized at the time of melting the glass, and the environment of the melting operation is not preferable. In addition, since the optical properties and thermal properties of the glass change according to the volatilization amount of the fluorine component, it is not easy to manage the melting conditions for suppressing variations in these properties.

Therefore, the present invention solves the drawbacks of the above-mentioned conventional phosphate optical glass, has a high refractive index, a high transmittance, and a low yield point, and is suitable for molding general lenses and aspheric lenses. Of course, it is an object to provide an optical glass suitable for molding a lens having a light wave control function having a nano-order level microstructure by precision mold press molding and other optical elements.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention considered the composition of the P ₂ O ₅ —Bi ₂ O ₃ —ZnO system in the production of glass, and antimony oxide Sb ₂ O. ₃ and alkali metal oxide R ₂ O were added and contained, and it was found that the above problems could be solved without containing fluorine F, and the present invention was completed.

That is, the optical glass of the present invention contains phosphorus, bismuth and zinc in terms of oxides, P ₂ O ₅ : 15 to 30 mol%, Bi ₂ O ₃ : 5 to 35 mol%, ZnO: 40 to 75 mol%. The first feature is that antimony is contained in an oxide equivalent of Sb ₂ O ₃ : 0.05 to 0.50 mol% and fluorine F is not contained.
In addition to the first feature, the optical glass of the present invention contains one or two or more alkali metal elements R in a total amount, in terms of oxide, R ₂ O: 2 to 15 mol%. This is the second feature.
Here, as the alkali metal element R, lithium, sodium, and potassium are representative elements. However, it contains rubidium and cesium in addition, and the metal element R of the first group is included in the category.
Further, in addition to the second feature, the optical glass of the present invention contains, as the alkali metal element R, lithium, sodium or potassium when the alkali metal element R is contained in an amount of more than 7 mol% in terms of oxide. A third feature is that it contains at least two alkali metal elements selected from the group consisting of:
The optical glass of the present invention has one or more of boron, silicon, and germanium in a total amount of 0.5 to 5 moles in terms of oxide, in addition to any of the first to third features. % Content is the fourth feature.
Further, the optical glass of the present invention has, as a fifth feature, in addition to any of the first to fourth features described above, the preform is a gob preform formed by dripping a glass melt. Yes.

Thus, by adjusting the composition of the P ₂ O ₅ —Bi ₂ O ₃ —ZnO-based glass and further containing appropriate amounts of antimony and alkali metal element R, the yield point can be lowered without containing fluorine F. The present inventors have found that, at a high refractive index, the degree of coloring of the glass is improved and the transmittance is increased. Furthermore, it has been found that the stability of the glass is improved and the occurrence of devitrification can be prevented by making the alkali metal element R at least two elements selected from lithium, sodium and potassium. . Further, it has been found that by containing an appropriate amount of one or more of boron, silicon, and germanium, the stability of the glass is further improved, and devitrification is less likely to occur. As a result, an optical glass having a yield point (At) of 431 ° C. to 493 ° C., a refractive index (n _d ) of 1.79 to 1.89, and a light transmittance at a wavelength of 400 nm of 70% or more was completed.
In the above description, the yield point (At) is the maximum point at which the expansion curve changes from rising to falling due to softening of the glass when the thermal expansion is measured by a thermomechanical analyzer (TMA). The refractive index (n _d ) refers to the refractive index of helium for the 587.6 nm emission line.

According to the optical glass of claim 1, since the composition described therein is used, an optical glass suitable for mold press molding including a precision mold press having a high refractive index, a high transmittance, and a low yield point is provided. It became possible to provide. Accordingly, it becomes possible to provide a lens having excellent optical characteristics, an aspherical lens, a lens having a nano-order level fine structure having an excellent light wave control function, and other optical elements.
Further, since fluorine F is not contained, the highly toxic fluorine component does not volatilize, and the environment for melting work is safer. Furthermore, the management of melting conditions is easier than when fluorine F is added.
According to the optical glass according to claim 2, in addition to the effects by the configuration described in claim 1, in a total amount of one or more of the alkali metal element R, in terms of oxide, R ₂ O : Since 2 to 15 mol% is contained, it is possible to make a glass having a lower yield point.
Moreover, according to the optical glass of Claim 3, in addition to the effect by the structure of the said Claim 2, when the alkali metal element R is contained more than 7 mol% in terms of oxide, the alkali metal element Since R includes at least two or more kinds of alkali metal elements selected from lithium, sodium, and potassium, it is possible to provide a glass having further excellent stability and resistance to devitrification.
According to the optical glass of claim 4, in addition to the effect of the structure of any of claims 1 to 3, the total amount of one or more of boron, silicon, and germanium is added to the oxide. Since it is contained in an amount of 0.5 to 5 mol% in terms of conversion, it is possible to obtain a glass having further improved stability and further excellent devitrification resistance.
According to the optical glass of claim 5, in addition to the effect of the structure according to any one of claims 1 to 4, the preform has a gob preform formed by dropping a glass melt. As a result, the reaction with the mold surface can be more effectively suppressed during precision molding, and a good and stable molded glass can be obtained without discoloring the glass surface by molding.

The components and their contents in the optical glass of the present invention will be described.
The component P ₂ O ₅ is a component for forming a glass network structure, and is an essential component for imparting stability that can be produced to glass.
P ₂ O ₅ is contained in an amount of 15 to 30 mol%. If it is less than 15 mol%, it becomes difficult to obtain a stable and good glass. On the other hand, when it exceeds 30 mol%, it is difficult to obtain a stable and good glass.
P ₂ O ₅ is preferably contained in an amount of 16.5 to 28.5 mol%, more preferably 18 to 27 mol%.

The component Bi ₂ O ₃ is a component for forming a glass network structure of the glass, and is essential for providing stability that can be produced to the glass, increasing the refractive index of the glass, and lowering the yield point.
Bi ₂ O ₃ is contained in an amount of 5 to 35 mol%. If Bi ₂ O ₃ is less than 5 mol%, it is difficult to obtain a stable and good glass, and if it exceeds 35 mol%, it is difficult to obtain a stable and good glass.
Bi ₂ O ₃ is preferably contained in an amount of 7.5 to 32.5 mol%, more preferably 10 to 30 mol%.

ZnO is an essential component effective for stabilizing the glass and lowering the yield point of the glass. ZnO is contained in an amount of 40 to 75 mol%.
If it is less than 40 mol%, it will be difficult to obtain a stable and good glass, and if it exceeds 75 mol%, it will be difficult to obtain a stable and good glass.
ZnO is preferably contained in an amount of 42.5 to 72.5 mol%, more preferably 45 to 70 mol%.

Note by any of _P 2 _{O 5} to _Bi 2 _{O 3} and ZnO is within the above range, vitrification becomes possible as a three-way system.

Sb ₂ O ₃ is effective and essential for improving the transmittance of glass. Sb ₂ O ₃ is contained in an amount of 0.05 to 0.50 mol%.
In many cases, Sb ₂ O ₃ is used in combination with nitrate or the like as a so-called clarifier, which usually removes fine bubbles in glass. However, in the present invention, Sb ₂ O ₃ plays a role of removing the factor of lowering the transmittance of the glass at a wavelength of 400 nm due to Bi ₂ O ₃ . This effect is also apparent from examples described later.
The reason why Sb ₂ O ₃ prevents a decrease in the transmittance of the glass is not always clear. But the presence of _Sb 2 _{O 3,} likely is _Bi 2 _{O 3} becomes higher oxidation state, whereby the transmittance decreases due due to the _Bi 2 _{O 3} in the 400nm is attributed to the fact that removal.
Even when antimony Sb is added in the form of Sb ₂ O ₅ , the same effect can be expected.
If Sb ₂ O ₃ is less than 0.05 mol%, the effect of improving the transmittance of the glass cannot be sufficiently obtained, and if it exceeds 0.50 mol%, the stability of the glass is impaired and stable and good. In addition, it is difficult to obtain a clear glass, and the effect of improving the transmittance of the glass is reduced.
Sb ₂ O ₃ is preferably contained in an amount of 0.07 to 0.47 mol%, more preferably 0.1 to 0.45 mol%.

R ₂ O is an effective component for lowering the yield point of glass. Here, R is at least one alkali metal element selected from alkali metal elements such as lithium, sodium, and potassium.
R ₂ O is contained in an amount of 2 to 15 mol%. If it is 2 mol% or less, the effect of lowering the yield point of the glass cannot be obtained sufficiently. If it exceeds 15 mol%, the stability of the glass is impaired, and it becomes difficult to obtain a stable and good glass.
R ₂ O is preferably contained in an amount of 3 to 12 mol%, more preferably 4 to 11 mol%.

R 2 _O is, in case of content exceeds 7 mol% of the R _{2 O,} lithium, sodium, by the consist of at least two or more types of alkali metal element selected from among potassium, alkali metal elements The stability of the glass due to the mixing effect is improved, and a good glass can be obtained.
Preferably, when contained in excess of 6.5 mol% of the R _{2 O,} R 2 _O is set to be at least two or more types of alkali metal element selected lithium, sodium, from potassium, more preferably When the R ₂ O content exceeds 6 mol%, the R ₂ O is composed of at least two kinds of alkali metal elements selected from lithium, sodium and potassium.
R ₂ O is more preferably composed of three kinds of alkali metal elements lithium, sodium, and potassium, so that the alkali mixing effect is further enhanced, the stability of the glass is further improved, and a good glass is obtained. be able to.

Components B ₂ O ₃ , SiO ₂ , and GeO ₂ are components for forming a glass network structure, and are effective for imparting further stability to the glass.
These are contained alone or in a total amount of 0.5 to 5 mol% in terms of oxide. If it is less than 0.5 mol%, it is difficult to obtain the effect of further stabilizing the glass. On the other hand, if the content exceeds 5 mol%, the glass becomes unstable and causes crystallization.
B ₂ O ₃ , SiO ₂ , and GeO ₂ are preferably contained in an amount of 0.75 to 4 mol%, more preferably 1 to 3 mol% in a total amount of one kind or two or more kinds.

In the present invention, it is preferable not to contain fluorine F. When fluorine F is contained, the fluorine component having toxicity at the time of melting the glass is likely to volatilize, so that the environment of the melting operation is not preferable, and variations in the optical properties and thermal properties of the glass are likely to occur. Furthermore, when producing a gob by droplet forming as a preform for molding, the fluorine concentration of the gob surface layer portion decreases due to the volatilization of the fluorine component, and this causes the yield point of the surface layer portion to be higher than that inside, and the mold If this is molded using a material, a problem of cracking from the surface layer portion is likely to occur.

In addition, as a specific example of a particularly preferable range in order to satisfy the object of the present invention, in terms of each component oxide,
P ₂ O ₅ : 20 to 26 mol%
Bi ₂ O ₃ : 12 to 18 mol%
ZnO: 47 to 53 mol%
Sb ₂ O ₃ : 0.1 to 0.4 mol%
Li ₂ O: 2 to 5 mol%
Na ₂ O: 2 to 5 mol%
K ₂ O: 2 to 5 mol%
(However, Li ₂ O, Na ₂ O, K ₂ O: 6 to 10 mol% in total)
B ₂ O ₃ : 1 to 3 mol%
There is.

By the way, the optical glass of this invention can make the form of the preform into the gob preform by dripping shaping | molding of a glass melt. With this gob preform, it is possible to produce a preform without polishing using water.
In the case of a preform that undergoes a polishing process, a hydrated layer is formed on the surface of the preform during the polishing process. This hydration layer causes Bi ₂ O ₃ in the glass to be reduced during molding, and component volatilization from the glass tends to occur. This has an adverse effect on aspherical molds or molds having nano-structures, and is one cause of discoloration of the molded glass surface.
In gob preforms that are not polished, a hydration layer is not formed on the surface, so that the reduction reaction of Bi ₂ O _{3 in} the glass can be suppressed. For this reason, the reaction with the mold surface can be more limited during the precision molding, so that the glass surface can be prevented from being discolored and a desired shape can be stably obtained.

Regarding the raw material for producing the optical glass in the embodiment of the present invention, for example, for the component P ₂ O ₅ , Zn (PO ₃ ) ₂ , R (PO ₃ ), P ₂ O ₅ , H ₃ PO _4, etc. are used. Can do.
For the component Bi ₂ O ₃ , Bi ₂ O ₃ , Bi (NO ₃ ) ₃ .5H ₂ O, or the like can be used.
For the component ZnO, ZnO and Zn (PO ₃ ) ₂ can be used.
Sb ₂ O ₃ and Sb ₂ O ₅ can be used for the component Sb ₂ O ₃ .
For the component R ₂ O, R ₂ CO ₃ , R (NO ₃ ), R (PO ₃ ) and the like can be used.
For the component B ₂ O ₃ , H ₂ BO ₃ , B ₂ O ₃ , BPO _{4 and the} like can be used.
For the component SiO ₂ , SiO ₂ or the like can be used.
For the component GeO ₂ , GeO ₂ or the like can be used.
The above raw materials are prepared and mixed so as to be in the component range described above, melted at 850 to 1200 ° C., homogenized through the steps of clarification (gas removal) and stirring, and then poured into a mold. After forming into a gob preform by molding or a dropping method, a homogeneous glass can be obtained by slow cooling.

The present invention will be further described below with reference to examples. The present invention is not limited in any way by these examples.
The raw materials were prepared and mixed so as to have the component compositions of Examples 1 to 11 and Comparative Examples 1 to 7 shown in Tables 1 to 3, and then put into a platinum crucible, and 1000 ° C. to 1200 ° C. in an electric furnace. After melting at a temperature of 0 ° C. and then holding at a temperature of 850 ° C. to 1000 ° C., it was poured into a mold and slowly cooled to obtain an optical glass.
About each obtained optical glass, the yield point (At) and the refractive index ( _nd ) were measured. Moreover, the transmission spectrum of glass was measured and the transmittance | permeability in wavelength 400nm was calculated | required.

In the examples and comparative examples, the yield point (At) was measured by heating a rod-shaped sample having a length of 15 to 20 mm and a diameter (side) of 3 to 5 mm at a constant rate of 10 ° C. per minute. It calculated | required from the thermal expansion curve obtained by measuring elongation and temperature. The refractive index (n _d ) was measured using the V block method. The transmission spectrum of the glass was measured with a spectrophotometer.
The measurement results are shown in Tables 1 to 3.

The results of measuring the liquid phase temperature for Examples 3, 6 to 11, and Comparative Example 7 are shown in Table 4. Here, the liquidus temperature is an equilibrium temperature between the melt state and the initial phase of the crystal. The lower the temperature, the more stable the glass melt, the less likely it is to devitrify, and the easier it is to obtain glass. The liquid phase temperature was measured using a melting furnace, and after raising the glass melt to the melting temperature, holding it at the evaluation temperature for 30 minutes or more, and then quickly removing it to check whether the glass melt was devitrified. This was done by observing.

As is apparent from Tables 1 to 3, since the glass of each of the examples of the present invention has a yield point in a relatively low temperature range of 431 to 493 ° C., molding is easy.
Furthermore, it has a high refractive index (n _d ) in the range of 1.79 to 1.89, a transmittance at a wavelength of 400 nm is 70% or more, and has a sufficient optical constant as an optical glass for precision molding. ing. From these, it can be seen that the glass of the present invention is a glass suitable for precision molding.

On the other hand, it can be seen that the glasses of Comparative Examples 1 to 6 have any problems such as high yield point (At), low transmittance, and low refractive index.
In addition, although the comparative example 1 is substantially equivalent to Example 1, it does not contain Sb ₂ O ₃ and the transmittance is less than 60%.
Comparative Example 2 is one containing no Sb ₂ O ₃ in Example 3, but the sag is lower, the transmittance is 60% or less.
The effects of containing Sb ₂ O ₃ and R ₂ O can be seen from Examples 1 and 3 and Comparative Examples 1 and ₂ .
Comparative Example 3 is an example in which the content of Sb ₂ O ₃ exceeds 0.50 mol%, and when Sb ₂ O ₃ exceeds 0.50 mol%, the transmittance is less than 70%, and the transmission It can be seen that the effect of improving the rate is not fully exhibited.
Comparative Example 4 and Comparative Example 5 correspond to Example 54 of Patent Document 1 and Example 3 of Patent Document 2, respectively. It can be seen that the yield point (At) is 492 ° C. or higher.
Example 1 has a yield point (At) of 493 ° C., which is substantially the same as Comparative Example 4. However, the refractive index in Example 1 is 1.89, which is higher than that in Comparative Example 4, and is more preferable.
Moreover, although the comparative example 6 is corresponded to Example 9 of patent document 3, it turns out that a yield point (At) is as high as 520 degreeC and the transmittance | permeability is 60% or less.
Furthermore, although the comparative example 7 contains the alkali metal element exceeding 7 mol% in terms of oxide, it is composed of only one kind of Na ₂ O, and devitrification occurs because the glass is unstable. It turns out that good glass cannot be obtained.
It can be seen that the glass shown in the above examples satisfies the three conditions of high refractive index, high transmittance, and low yield point.

Further, from Table 4, it can be seen that in Comparative Example 7, the liquidus temperature is as high as 825 ° C. and unstable, but in the Examples, the liquidus temperature is lowered due to the alkali mixing effect and the glass is stable. Further, it can be seen that, among the examples, those containing B ₂ O ₃ , SiO ₂ , or GeO ₂ can further lower the liquidus temperature and obtain a more stable glass.

The optical glass of the present invention is industrially applicable as an optical glass suitable for precision molding such as an aspherical lens and a light wave control glass with a high refractive index, a high transmittance, and a low yield point.

Claims

Phosphorus, bismuth and zinc in terms of oxides
P 2 O 5 : 15-30 mol%
Bi 2 O 3 : 5 to 35 mol%
ZnO: 40 to 75 mol%
And antimony in terms of oxide,
Sb 2 O 3 : 0.05 to 0.50 mol%
An optical glass which is contained and does not contain fluorine F.
1 type or 2 types or more of alkali metal elements R in total amount, in terms of oxides,
R 2 O: 2 to 15 mol%
The optical glass according to claim 1, wherein the optical glass is contained.
When the alkali metal element R is contained in excess of 7 mol% in terms of oxide, the alkali metal element R includes at least two or more kinds of alkali metal elements selected from lithium, sodium, and potassium. The optical glass according to claim 2.
One or more of boron, silicon, and germanium in total amount, in terms of oxide,
B 2 O 3 , SiO 2 , GeO 2 : 0.5 to 5 mol%
The optical glass according to any one of claims 1 to 3, wherein the optical glass is contained.
5. The optical glass according to claim 1, wherein the preform is a gob preform formed by dropping a glass melt.