JP3255390B2 - Low melting point optical glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low melting point optical glass which can be pressed at a low temperature and an optical product obtained by using the glass. Various optical products including lenses can be obtained by precision-pressing the low-melting optical glass of the present invention, but the low-melting optical glass of the present invention is particularly capable of aspherical precision press, and has a low melting point of the present invention. An aspheric lens can be obtained by precision pressing using optical glass.

[0002]

DISCLOSURE OF THE BACKGROUND OF INVENTION Problems to be Solved] The glass of high refractive index and high dispersion region in a conventional optical glass, for example, P ₂ O as disclosed in JP-A-52-132012 _{5 -B 2 O 3 -Nb 2 O} 5 - P 2 O is disclosed in glass and Sho 56-40094 discloses an alkali metal oxide ₅ -Nb ₂ O ₅ - glass of alkali metal oxide is there.

However, these glasses have a high deformation point (Ts) of 580 ° C. or more, while precision press molding is usually performed at a temperature about 50 ° C. higher than the deformation point (Ts). When glass is used for precision press molding, the temperature at the time of pressing needs to be 630 ° C. or higher. However, if the press is repeated at such a high temperature, the mold material is significantly deteriorated, a precise glass surface cannot be obtained, the mold is frequently replaced, and mass production of precision lenses becomes very difficult. Therefore, in order to improve the yield of precision press lens production, it is necessary to lower the yield point (Ts) of the glass to be formed.

[0004] These glasses have a liquidus temperature (L.
T) is also high, which is also a cause that is not suitable for precision press molding.

[0005] Apart from the above-mentioned glass, as an optical glass having a high refractive index, a high dispersion and a low melting point, there is disclosed in
No. 1233, SiO ₂ —GeO ₂ —
There is TiO ₂ —Nb ₂ O ₅ —alkali metal oxide glass.

However, the glass described in JP-A-5-51233 has a glass yield point (Ts) of 550 ° C.
However, the liquidus temperature (LT) is high and the devitrification tendency near the softening point is strong. For this reason, it is difficult to heat the glass preform to soften it and perform precision press molding, which is not suitable for manufacturing a pressed lens.

Accordingly, a first object of the present invention is to provide a high-refractive-index and high-dispersion property and press molding at a relatively low temperature near the glass softening point without devitrification of the glass. Another object of the present invention is to provide an optical glass having a low liquidus temperature (LT) and excellent stability.

A second object of the present invention is to provide an optical product obtained by precision pressing the above-mentioned low melting point optical glass.

[0009]

Low melting optical glass of the present invention to achieve the above first object, according to an aspect of, as a first aspect, and in weight%, P ₂ O ₅ and 14 to 32%, B 0.5 to 16% of ₂ O ₃ , 18 to 52% of Nb ₂ O ₅ , Li ₂ O
The 0.3 to 6%, from 5.5 to 22% of Na ₂ O and Si
O ₂ and characterized in that it comprises less than 0.1% to 5%.

In a second aspect, the low melting point optical glass of the present invention that achieves the first object has a P ₂ O ₅ content of 14 to 32% and a B ₂ O ₃ content of 0 to 32% by weight. .5-16
% Nb ₂ O ₅ of 18-52%, the Li ₂ O 0.3 to 6
%, 0.3 to Na ₂ O of from 5.5 to 22% and WO ₃
It is characterized by containing 12%. Hereinafter, the present invention will be described in detail.

In a first embodiment of the present invention, the refractive index (nd) is in the range of 1.70 to 1.77, and the dispersion is 32 to 23.
The present invention provides a low melting point optical glass having a glass deformation point (Ts) of 570 ° C. or less, and its constituent components and the reason for limiting the content thereof are as follows.

P ₂ O ₅ is an indispensable component as a glass forming component in phosphate glass. Phosphate glass is capable of melting glass at a lower temperature than silicate glass, and is characterized by high transmittance in the visible region. Since the component P ₂ O ₅ which is located in a highly dispersed side as compared to SiO ₂ or B ₂ O ₃ is the same glass-forming oxide component, in order to obtain the Abbe number 32 following optical characteristics, P ₂ O ₅ Should be at least 14%. Conversely, if it exceeds 32%, the devitrification becomes strong and high refractive index characteristics cannot be obtained. Therefore, the content of P ₂ O ₅ in the glass of the first embodiment is 14 to 32.
%. The preferred P ₂ O ₅ content is 16
-30%.

B ₂ O ₃ has a very good devitrification resistance when added in an appropriate amount to a phosphate glass, and P ₂ O ₅ , Si
The effect of lowering the glass yield point (Ts) is greater than other glass-forming oxides such as O ₂ . Therefore, B ₂ O ₃
Is an essential component of the glass of the first aspect of the present invention. When the content of B ₂ O ₃ is less than 0.5%, the devitrification resistance of the glass is deteriorated as described above, and the yield point (Ts) of the glass is increased. Dispersion characteristics cannot be obtained. For this reason, in the glass of the first embodiment, B ₂ O ₃ is limited to the range of 0.5 to 16%. The content of the preferred B ₂ O ₃ is in the range 1 to 14%.

Nb ₂ O ₅ is a component that is indispensable for obtaining the desired high refractive index and high dispersion characteristics, and a component that has the effect of increasing the durability. If Nb ₂ O ₅ is less than 18%, the desired high refractive index and high dispersion characteristics cannot be obtained. If it exceeds 52%, the devitrification resistance of the glass deteriorates and the glass yield point (Ts) decreases. To rise. Therefore Nb ₂ O ₅ in the glass of the first aspect is limited to the range of 18-52%. The preferred Nb ₂ O ₅ content is 20 to
It is in the range of 52%.

Li ₂ O and Na ₂ O are indispensable components for reducing the target glass yield point (Ts) to 570 ° C. or lower. Li ₂ O is less than 0.3%, Na ₂ O is 5.5%
If it is less than the above, the above object cannot be achieved. Li ₂ O
Exceeds 6% and Na ₂ O exceeds 22%, the desired high refractive index characteristics cannot be obtained. Therefore, in the glass of the first embodiment, Li ₂ O is in the range of 0.3 to 6%, and Na is Na.
₂ O is limited to a range of 5.5 to 22%. Preferred L
i ₂ O The content in the range 0.3 to 5%, and the content of Na ₂ O in the range of 5.5 to 20%.

In the glass of the first embodiment of the present invention, SiO.sub.2 is a glass having a devitrification resistance, particularly a molding temperature (liquid phase temperature L.P.
T) is an indispensable component because the effect of lowering the viscosity at the liquidus temperature (LT) and increasing the viscosity at the liquidus temperature (LT) to make the glass less likely to devitrify is very large. If the content of SiO ₂ is less than 0.1%, it is difficult to form a glass lump by molding a target molten glass, and to precisely press the glass lump to obtain an optical product. If the content of SiO ₂ is 5% or more, the desired high refractive index characteristics cannot be obtained, and the glass yield point (T
s) increases. Thus, in the glass of the first aspect of the present invention, SiO ₂ is limited to less than 0.1% to 5%, preferably in the range of 1% to 4.5%.

In the glass according to the first aspect of the present invention, by adding an appropriate amount of MgO, CaO, SrO, and BaO as optional components, the liquidus temperature (LT) of the glass can be lowered and the stability can be increased. it can. However, MgO exceeds 5%, CaO exceeds 5%, SrO exceeds 5%, and Ba
If O exceeds 16%, the desired high refractive index and high dispersion properties cannot be obtained, and the devitrification resistance also deteriorates. For this reason, Mg
The contents of O, CaO, SrO, and BaO are each 0-5.
%, 0 to 5%, 0 to 5%, and 0 to 16%. Preferably, MgO is in the range of 0-3% and CaO
Is in the range of 0-3%, SrO is in the range of 0-3%,
aO ranges from 0 to 14%.

In the glass of the first embodiment of the present invention, a high refractive index and a high dispersion property can be given to the glass by adding an appropriate amount of TiO ₂ as an optional component.
If it exceeds 2%, the devitrification resistance becomes poor, the yield point (Ts) of the glass increases, and the glass is strongly colored. Therefore the content of TiO ₂ is limited to 0-12%. Preferred T
The content of the iO ₂ is in the range of 0 to 10%.

In the glass of the first embodiment of the present invention, an effect of lowering the yield point (Ts) of the glass can be obtained by adding an appropriate amount of K ₂ O as an optional component. High refractive index characteristics can not be obtained,
The devitrification resistance also deteriorates. Therefore, the content of K ₂ O is from 0 to 12
%. The content of the preferred K ₂ O is in the range of 0%.

In the glass according to the first embodiment of the present invention, the refractive index of the optional components ZnO, Al ₂ O ₃ and Ta ₂ O ₅ can be adjusted by adding an appropriate amount.
If Al ₂ O ₃ exceeds 5% and Ta ₂ O ₅ exceeds 5%, the devitrification resistance deteriorates. Therefore ZnO is 0 to 5%, Al ₂ O ₃ is 0 to 5%, Ta ₂ O ₅ is limited to 0-5%. Preferably ZnO is 0~3%, Al ₂ O ₃ is 0 to 3%, Ta ₂
O ₅ is in the range of 0-3%.

In the glass of the first embodiment of the present invention, optional components As ₂ O ₃ and Sb ₂ O ₃ are effective as a decolorizing agent and a fining agent. However, if any of them exceeds 2%, the devitrification resistance deteriorates. Therefore, As ₂ O
Content of ₃ and Sb ₂ O ₃ content _of is limited to the range of 0-2%, respectively.

GeO ₂ as an optional component can be used to adjust the refractive index by adding an appropriate amount of GeO _{2 as} an optional component in the glass of the first embodiment of the present invention.
%, The deformation point (Ts) of the glass increases, the desired glass deformation point (Ts) of 570 ° C. or less cannot be obtained, and the high refractive index property cannot be obtained. Therefore,
GeO ₂ is used in the glass of the first embodiment of the present invention in the range of 0 to 5;
%. Preferably, it is in the range of 0 to 3%.

In the glass of the first embodiment of the present invention, when an appropriate amount of WO ₃ is added as an optional component, there is an effect of lowering the yield point (Ts) of the glass. However, when WO ₃ exceeds 12%, the devitrification resistance deteriorates. Thus, WO ₃ in the glass of the first aspect of the present invention is limited to a range from 0 to 12%. Preferably, it is in the range of 0 to 9%.

In the glass according to the first aspect of the present invention,
Further, La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Cs ₂ O,
Components such as ZrO ₂ , PbO, and SnO ₂ can be added as long as the object of the present invention is not impaired.

Next, a second embodiment of the present invention will be described. In a second embodiment of the present invention, the refractive index (nd) is 1.77.
To provide a low-melting optical glass having a dispersion ratio in the range of 28 to 20 and a glass yield point (Ts) of 570 ° C. or less, the constituent components and the content thereof. The reason for the limitation is as follows.

In the glass according to the second embodiment of the present invention,
₂ O ₅ is an indispensable component as a glass forming component in phosphate glass, and the content of P ₂ O ₅ is limited to the range of 14 to 32% for the same reason as in the glass of the first embodiment. The content of the preferred P ₂ O ₅ is in the range of 16-30%.

In the glass according to the second aspect of the present invention,
₂ O ₃ is first aspect improving Similarly devitrification resistance as in the glass of the present invention, an essential component for lowering the glass deformation point (Ts), the content of B ₂ O ₃ is , The first
For the same reason as in the glass of the embodiment,
Limited to a range of 16%. The content of the preferred B ₂ O ₃ is in the range 1 to 14%.

In the glass according to the second embodiment of the present invention,
b ₂ O ₅ is an essential component for obtaining a high refractive index and a high dispersion property and for improving durability, and the content of Nb ₂ O ₅ is the same as in the glass of the first embodiment. , The range is limited to 18 to 52%. Preferred Nb
The content of the ₂ O ₅ is in the range of 20-50%.

In the glass according to the second embodiment of the present invention,
i ₂ O and Na ₂ O are components indispensable for reducing the target glass yield point (Ts) to 570 ° C. or lower. For the same reason as in the glass of the first embodiment, Li ₂ O and Na ₂ O are used.
O of content in the range of 0.3 to 6%, the content of Na ₂ O 5.
It is limited to the range of 5 to 22%. The preferred Li ₂ O content is in the range of 0.3-5%, and the Na ₂ O content is 5.5-2%.
The range is 0%.

WO ₃ is an indispensable component in the second aspect of the present invention, because when added to the glass of the second aspect of the present invention in an appropriate amount, the effect of lowering the yield point (Ts) of the glass is very large. In the glass according to the second aspect of the present invention,
If O ₃ is less than 0.3%, the desired properties of a glass yield point of 570 ° C. or less cannot be obtained, and if it exceeds 12%, the devitrification resistance deteriorates. Therefore, WO ₃ is limited to the range of 0.3 to 12% in the glass of the second embodiment of the present invention. Preferably it is in the range of 2 to 9%.

In the glass according to the second embodiment of the present invention,
As an optional component, a decrease in the liquidus temperature (LT) of the glass,
MgO, CaO, SrO, Ba contributing to improvement of stability
O is 0-5%, 0-5%, 0-5%, 0-16
% Can be added. MgO, CaO, SrO, Ba
O content is 0-3%, 0-3%, 0-3%, respectively.
A range of 0 to 14% is preferred.

Also in the second embodiment of the present invention, TiO ₂ for imparting a high refractive index and a high dispersion property to glass, and K ₂ O for lowering the glass yield point (Ts) may be added as optional components. possible, the content of TiO ₂ for the same reason as the case of the glass of the first aspect in the range from 0 to 12% content of K ₂ O is limited to a range from 0 to 12%. The content of the preferred TiO2 is in the range of 0-10%, preferable content of K ₂ O is in the range of 0%.

In the glass of the second embodiment of the present invention,
ZnO, Al ₂ O ₃ and Ta ₂ O ₅ can be added as optional components for adjusting the refractive index. However, as in the case of the glass of the first embodiment, ZnO, Al ₂ O ₃ and Ta ₂ O ₅ can be added. The content is limited to the ranges of 0 to 5%, 0 to 5%, and 0 to 5%, respectively. _{ZnO, Al 2 O 3, Ta} 2 O preferred content respectively 0-3% of _5, 0-3%, in the range of 0-3%.

In the glass of the second aspect of the present invention,
As ₂ O ₃ and Sb ₂ O ₃ are effective as decolorizers and fining agents. However, if any of them exceeds 2%, the devitrification resistance deteriorates. Therefore, As ₂ O ₃ and Sb ₂
The content of O ₃ is limited to the range of 0-2%, respectively.

In the glass of the second embodiment of the present invention, if a small amount of SiO ₂ is added as required, the devitrification resistance of the glass can be improved. However, if the content of SiO ₂ is 5% or more, the desired high refractive index characteristics cannot be obtained. Therefore, in the second embodiment of the present invention, SiO ₂ is 0 to 5
%. Particularly preferably, it is 0 to 4.5.
% Range.

In the glass according to the second embodiment of the present invention,
La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Cs ₂ O, ZrO
Components such as ₂ , PbO and SnO ₂ can be added within a range not to impair the object of the present invention.

In the glass of the second embodiment of the present invention, if GeO ₂ is added, the desired refractive index (n
d) Since high refractive index characteristics of 1.77 to 1.85 or low melting point characteristics of glass deformation point (Ts) of 570 ° C. or less cannot be obtained, unlike the glass of the first embodiment, GeO
₂ cannot be added in the glass of the second embodiment.

As a raw material of the low melting point optical glass of the present invention (meaning the glass of the first embodiment and the glass of the second embodiment; the same applies hereinafter), as for P ₂ O ₅ , orthophosphoric acid (H
₃ PO ₄ ), metaphosphate, diphosphorus pentoxide, and the like, and as other components, carbonates, nitrates, oxides, and the like can be appropriately used. These raw materials are weighed to a desired ratio and mixed to obtain a prepared raw material.
By throwing it into a melting furnace heated to 0 ° C, melting, refining, stirring, homogenizing, then casting it into a mold and slowly cooling it,
The low melting point optical glass of the present invention can be obtained.

The optical product of the present invention can be obtained by precision pressing the low melting point optical glass of the present invention. Known methods and apparatuses can be used for the precision press, and the conditions can be appropriately determined in consideration of the composition and physical properties of the glass. A particularly preferred optical product is an aspherical lens obtained by aspherical precision pressing of the low melting point optical glass of the invention.

The precision press can be performed using, for example, a press apparatus as shown in FIG. The apparatus shown in FIG. 1 is obtained by placing a mold having an upper mold 1, a lower mold 2 and a guide mold 3 on a support base 10 provided on a support rod 9, and winding a heater 12 around the outer periphery of the mold. It is provided in the tube 11. The molded glass lump 4 made of the low melting point optical glass of the present invention is disposed between the upper mold 1 and the lower mold 2. The molded glass lump 4 is, for example, a sphere having a diameter of about 2 to 20 mm. The size of the spherical object is appropriately determined in consideration of the size of the final product.

After the molded glass block 4 is placed between the upper mold 1 and the lower mold 2, the heater 12 is energized to heat the inside of the quartz tube 11. The temperature in the mold is monitored by a thermocouple 14 inserted inside the lower mold 2. The heating temperature is a temperature at which the viscosity of the non-formed glass block 4 is suitable for precision press, for example, about 10 ⁸ to 10 ⁹ poise. After the temperature reaches a predetermined temperature, the push rod 13 is lowered to push the upper mold 1 from above, thereby pressing the glass lump 4 in the molding mold. The pressure and time of the press can be appropriately determined in consideration of the viscosity of the glass and the like. For example, the pressure is 50 to 100 kg /
cm ² and the time can be 10 to 120 seconds. After pressing, gradually cool to the glass transition temperature, then rapidly cool to room temperature, and remove the molded product from the molding mold,
The optical product of the present invention can be obtained.

[0042]

The present invention will be further described below with reference to examples. Examples 1 to 11 and Comparative Example 1 The low-melting-point optical glasses of Examples 1 to 11 were prepared by a conventional method according to the prepared compositions (% by weight) shown in Tables 1 and 2. That is, as a raw material, P ₂ O ₅ is orthophosphoric acid (H ₃ PO
₄ ), using metaphosphate or diphosphorus pentoxide, etc., and using other components such as carbonates, nitrates, oxides, etc., weigh these raw materials in a desired ratio, mix them to form a blended raw material, This was put into a melting furnace heated to 1000 ° C. to 1200 ° C., melted, clarified, stirred, homogenized, and then slowly cast into a mold to obtain a low-melting optical glass of Examples 1 to 11. . The glasses of Examples 1 to 6 correspond to the glass of the first embodiment of the present invention, and the glasses of Examples 7 to 11 correspond to the glass of the second embodiment of the present invention.

Further, GeO was added to the glass composition of the ninth embodiment.
A glass of Comparative Example 1 was produced in the same manner as in Example 9 except that 10% by weight of ₂ was added.

The optical performance of the obtained glass is shown in Tables 1 and 2. Refractive index (nd) and Abbe number (νd) in the table
Shows the results when the slow cooling rate was set to -30 ° C./hr. The glass yield point (Ts) is 8 ° C using a thermal expansion measuring device.
This is the result when the temperature was raised at / min. The liquidus temperature (LT) was kept in a devitrification test furnace having a temperature gradient of 400 ° C. to 1050 ° C. for 30 minutes, and the presence or absence of crystals was observed with a microscope of 80 × magnification. The permeability is also a result of visual observation at the same time as the liquidus temperature measurement.

[0045]

[Table 1]

[0046]

[Table 2]

Comparative Examples 2 to 5 The glasses of Comparative Examples 2 to 5 were P ₂ O ₅ —B ₂ O ₃ — produced according to Examples Nos. 10, 15, 17, and 21 of JP-A No. 52-132012. It is an Nb ₂ O ₅ -alkali metal oxide-based glass, and the composition of these glasses is shown in Table 3. Further, the refractive index (nd), Abbe number (νd), liquidus temperature (LT), glass yield point (T
Table 3 also shows the results of measuring s).

[0048]

[Table 3]

Comparative Examples 6 to 9 The glasses of Comparative Examples 6 to 9 were P ₂ produced according to Examples Nos. 1, 4, 7, and 14 of JP-B-56-40094.
O ₅ -Nb ₂ O ₅ - an alkali metal oxide glass, the composition of these glasses are shown in Table 4. Table 4 also shows the measurement results of the refractive index (nd), Abbe number (νd), liquidus temperature (LT), and glass yield point (Ts) of these glasses.

[0050]

[Table 4]

Comparative Examples 10 to 16 The glasses of Comparative Examples 10 to 16 were SiO ₂ -GeO ₂ prepared according to Examples Nos. 1, 2, 3, 4, 5, 6, and 8 of JP-A-5-51233. -TiO ₂ -Nb ₂ O ₅ -
It is an alkali metal oxide glass, and the composition of these glasses is shown in Table 5. Table 5 also shows the measurement results of the refractive index (nd), Abbe number (νd), liquidus temperature (LT), and glass yield point (Ts) of these glasses.

[0052]

[Table 5]

When the physical properties of the glasses of Examples 1 to 11 shown in Tables 1 and 2 are compared with the physical properties of the glasses of Comparative Examples 1 and 2 to 16 shown in Table 2, The following is clear.

(I) Examples 1 to 1 shown in Tables 1 and 2
(1) The glass of the present invention has a refractive index (nd) of 1.70 to
It is a low melting point optical glass having a high refractive index and a high dispersion, having a range of 1.85 and an Abbe number (νf) of 32 to 20. Furthermore, the glass of the present invention of Examples 1 to 11 has a glass deformation point (Ts) of 570 ° C. or less, a liquidus temperature (LT) of all glass of 930 ° C. or less, and a temperature of 30 ° C. near the softening point. The glass did not devitrify when held for minutes. Therefore, these glasses have a stability that enables mass production of lenses by precision pressing.

On the other hand, the glass of Comparative Example 1 was obtained by adding 10% by weight of GeO ₂ to the glass composition of Example 9, but the glass yield point was lower than that of Example 9. Since (Ts) rises by 30 ° C. and the refractive index (nd) drops greatly, it is not preferable to add GeO ₂ to the glass of the second embodiment of the present invention.

(Ii) The glasses of Comparative Examples 2 to 5 shown in Table 3 are the glasses of the first embodiment of the present invention (for example, Examples 1 to 6).
Compared with the composition of (a), the liquid phase temperature is as high as 960 to 1020 ° C. because it does not contain SiO ₂ , and a glass lump is molded from molten glass, and the obtained glass lump is softened to produce a precision press lens. It is very difficult.

In comparison with the glass of the second embodiment of the present invention, the glasses of Comparative Examples 2 to 4 mainly use Nb ₂ O ₅ and TiO ₂ in order to give high refractive index characteristics. However, since it does not contain WO ₃ , the glass yield point is high. Further, although the glass of Comparative Example 5 contains WO ₃ ,
Since it also contains eO ₂ , the glass yield point (Ts) is high and the refractive index (nd) is lower than the refractive index (nd) of the glass of the second embodiment of the present invention in the range of 1.77 to 1.85. It becomes something.

(Iii) The glasses of Comparative Examples 6 to 9 shown in Table 4 have poor devitrification resistance and have a glass yield point (Ts) because only P ₂ O ₅ is used as the glass-forming oxide. high.
Further, since only K ₂ O is used as the alkali metal oxide having the highest effect in lowering the sag point of the glass, the sag point of the glass is high, which is not practical as a glass for precision press molding.

(Iv) In the glasses of Comparative Examples 10 to 16 shown in Table 5, the glass was devitrified during the melting of the glass, or the glass was cast after melting, and the liquidus temperature (LT) was obtained. Is high as 1000 ° C. or higher, and if kept near the softening point for 30 minutes, the glass is devitrified, and none of them is practical.

Example 12 Using the glass of Example 2, an aspherical lens was obtained by performing an aspherical precision press using the press apparatus shown in FIG.

Example 2 of a spherical object having a diameter of 2 to 20 mm
After placing the glass between the upper mold 1 and the lower mold 2, the inside of the quartz tube 11 was heated by turning on the heater 12 with a nitrogen atmosphere in the quartz tube 11. After the temperature in the molding mold is set to 570 ° C. at which the viscosity of the glass lump to be molded becomes about 10 ⁸ to 10 ⁹ poise, the push rod 13 is lowered to push the upper mold 1 from above while maintaining this temperature. The glass mass to be molded in the molding mold was pressed. The pressing pressure was 80 kg / cm ² , and the pressing time was 30 seconds. After the pressing, the pressure of the pressing is released, and the glass molded body formed by the aspherical pressing is removed from the upper mold 1.
And a glass transition temperature of 4 while being in contact with the lower mold 2.
The glass was gradually cooled to 95 ° C., then rapidly cooled to around room temperature, and the aspherical glass was removed from the mold. The obtained aspherical lens was an extremely accurate lens.

[0062]

According to the present invention, there is provided a low-melting optical glass having a high refractive index and a high dispersion property, a low glass yield point, a stable devitrification resistance, and an excellent moldability. can do. Furthermore, by using the low melting point optical glass of the present invention, it is possible to produce a lens while extending the life of a molding die for precision press. Also,
Optical products such as aspheric lenses can be obtained by precision pressing using the low melting point optical glass of the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a precision press device for producing an optical product of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper mold 2 Lower mold 3 Guide mold 4 Glass lump to be molded 9 Support rod 10 Support base 11 Quartz tube 12 Heater 13 Push rod 14 Thermocouple

Claims (10)

(57) [Claims] 2. A method according to claim 1, wherein said P ₂ O ₅ is from 14 to 32, expressed as% by weight.
% B ₂ O ₃ and 0.5 to 16%, the Nb ₂ O ₅ 18~52
%, The Li ₂ O 0.3 to 6%, a Na ₂ O from 5.5 to 22%
A low melting point optical glass containing 0.1 to less than 5% of SiO _2, having a deformation point of 570 ° C. or less and a liquidus temperature of 930 ° C. or less. 2. A low-melting optical glass according to claim 1, characterized in that used for precision press. 3. The composition further comprises 0-5% of MgO and 0-5% of CaO.
5%, SrO 0-5%, BaO 0-16%, TiO
The low-melting optical glass according to claim 1, comprising 0 to 12% of ₂ and 0 to 12% of K ₂ O. 4. A further 0-5% of ZnO, the _{Al 2 O 3 0~5%, Ta} 2 O 5 0-5% of As ₂ O ₃ 0 to 2%
Sb ₂ O ₃ 0-2% low melting optical glass according to any one of claims 1 to 3 GeO ₂ 0 to 5% and that WO ₃ and characterized in that it comprises 0-12%. 5. The P ₂ O ₅ , expressed in% by weight, is 14 to 32.
% B ₂ O ₃ and 0.5 to 16%, the Nb ₂ O ₅ 18~52
%, The Li ₂ O 0.3 to 6%, a Na ₂ O from 5.5 to 22%
And WO ₃ hints from 0.3 to 12%, the yield point of the glass is not less 570 ° C. or less, the low-melting-point optical glass, wherein a liquidus temperature of 930 ° C. or less. 6. The low-melting optical glass according to claim 5, characterized in that used for precision press. 7. Further, 0-5% of MgO and 0-0 of CaO.
5%, SrO 0-5%, BaO 0-16%, TiO
₂ a low melting point optical glass according to claim 5 or 6, characterized in that it comprises 0-12% 0 to 12%, and K ₂ O. 8. The composition further comprises 0-5% of ZnO and 0% of Al ₂ O ₃ .
To 5% Ta ₂ O ₅ 0-5% of As ₂ O ₃ 0~2%, S
b ₂ O ₃ 0-2% and the low-melting-point optical glass according to any one of claims 5-7 for the SiO ₂ characterized in that it comprises 0 to less than 5%. 9. An optical product obtained by precision-pressing the low-melting-point optical glass according to claim 1. 10. The optical product according to claim 9, which is an aspheric lens.