JP3252152B2 - Low melting point optical glass and optical products - 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 optical glass which can be pressed at a low temperature and an optical product using the glass. The low-melting-point optical glass of the present invention can be subjected to aspherical precision pressing, and an aspherical lens can be obtained by precision pressing using the low-melting-point optical glass of the present invention.

[0002]

2. Description of the Related Art Among conventional optical glasses, glass having a high refractive index and a high dispersion region is disclosed, for example, in Japanese Patent Publication No. 55-375.
No. 00 are disclosed in Japanese _{P 2 O 5 -B 2 O 3} -Nb
₂ O ₅ -alkali metal oxides and JP-B-56-4009
There is a P ₂ O ₅ —Nb ₂ O ₅ alkali metal oxide-based glass disclosed in Japanese Patent Publication No. However, these glasses have a high glass yield temperature (Ts) of 580 ° C. or higher,
On the other hand, precision press molding is usually performed at a temperature about 50 ° C. higher than the yielding temperature (Ts). Therefore, when these glasses are used for precision press molding, they are pressed at a temperature of 630 ° C. or higher. However, when the press is repeated at such a relatively 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 temperature (Ts) of glass. Furthermore, these glasses also have a high liquidus temperature (LT), which also makes them unsuitable for precision press molding.

[0003]

[0007] Apart from the above-mentioned glass, an optical glass having a high refractive index, a high dispersion and a low melting point is disclosed in JP-A-5-51233.
_{SiO 2 -GeO 2 -TiO 2 -Nb 2} O 5 - there is a glass of the alkali metal oxide. However, Japanese Patent Application Laid-Open
The glass described in JP-A-51233 has a low glass deformation temperature of 550 ° C. or lower, but has a high liquidus temperature (LT).
There is also a strong tendency to devitrify near the softening point. 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, an object of the present invention is to provide a high-refractive-index and high-dispersion property, press molding at a relatively low temperature near the glass softening point without devitrification of the glass, An object of the present invention is to provide an optical glass having a low temperature and excellent stability. In particular, the present invention has a refractive index of 1.7.
In the range of 3 to 1.84, the dispersion ratio is in the range of 29 to 23, the glass yield point (Ts) is 570 ° C. or less,
Moreover, it is an object of the present invention to provide a low-stability optical glass with excellent stability (excellent devitrification resistance) that enables press molding without devitrification even at a relatively low temperature near the glass softening point. And

Still another object of the present invention is to provide an optical product obtained by precision pressing the above-mentioned low melting point optical glass. In particular, an object of the present invention is to provide an aspheric lens obtained by aspherical precision press of the above-mentioned low melting point optical glass.

[0006]

Low melting optical glass of the present invention According to an aspect of _{the, P 2 O 5 16~38% B} 2 O 3 1~20% Nb 2 O 5 14 to display the content of each component in percent by weight ~44% PbO 7~26% WO ₃ below 1~20% TiO ₂ 0~10% (however, exceed _{TiO 2 + WO 3 5%,} 2
_{2%) Li 2 O 0~5% Na 2} O 0~18% K 2 O 0~13% ( _{however, Li 2 O + Na 2 O} + K 2 O 6~20
%).

The low melting point optical glass of the present invention further comprises Ca
O, SrO, BaO, GeO ₂ , TaO ₂ , ZnO, A
At least one of s ₂ O ₃ and Sb ₂ O ₃ may be included. The contents of these components are expressed in weight%,
0-5% of CaO, 0-5% of SrO, Ba
O is 0% GeO ₂ is 0% Ta ₂ O ₅ is Less than six% ZnO is 0 to 4% As ₂ O ₃ 0-2%
Sb ₂ O ₃ is 0-2%.

Further, the present invention provides an optical product obtained by precision pressing the low melting point optical glass of the present invention,
In particular, the present invention relates to an aspheric lens obtained by aspherical precision pressing of the low melting point optical glass of the present invention. The reasons for limiting each component and its content in the low melting point optical glass of the present invention will be described below.

[0009] P ₂ O ₅ is an essential component as a glass forming component in phosphate glass. Phosphate glass is capable of dissolving 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 29 following optical characteristics, P ₂ O ₅ Should be at least 16%. On the other hand, if it exceeds 38%, the devitrification becomes strong and high refractive index characteristics cannot be obtained. Therefore P
The content of the ₂ O ₅ is limited to the range of 16-38%. The content of the preferred P ₂ O ₅ is in the range of 18-36%.

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, it is an indispensable component for the glass of the present invention. When the content of B ₂ O ₃ is less than 1%, the devitrification resistance of the glass deteriorates as described above, and the yield point (Ts) of the glass increases. When the content exceeds 20%, the desired high refractive index and high dispersion characteristics are obtained. Can not be obtained. Therefore B ₂ O ₃ is limited to a range of 1-20%. The content of the preferred B ₂ O ₃ is in the range from 2 to 18%.

Nb ₂ O ₅ is a component indispensable for obtaining the intended high refractive index and high dispersion characteristics, and is a component having an effect of improving durability. If Nb ₂ O ₅ is less than 14%, the desired high refractive index and high dispersion characteristics cannot be obtained. If it exceeds 44%, the devitrification resistance of the glass deteriorates, and the yield point (Ts) of the glass becomes low. Rises. Thus, Nb ₂ O ₅ is limited to the range of 14-44%. The content of the preferred Nb ₂ O ₅ is a range of 16-42%.

PbO is required to be at least 7% in order to have the desired high refractive index characteristics and the effect of lowering the glass yield point (Ts). If it exceeds 26%, the desired high dispersion characteristics cannot be obtained. Therefore, PbO is 7 ~
It is limited to a range of 26%. The preferred PbO content is 9
２４24%.

WO ₃ lowers the glass yield point (Ts) as compared with the components having the desired high refractive index and high dispersion characteristics and other high refractive index and high dispersion characteristics such as TiO ₂ and Nb ₂ O _5. To be effective, at least 1% is needed. On the other hand, if it exceeds 20%, the devitrification resistance deteriorates, and the glass is strongly colored. Therefore, the content of WO ₃ is 1 to
Limited to 20%. The preferred WO ₃ is content 2-18
% Range.

TiO ₂ is a component having a large effect of obtaining a high refractive index and a high dispersion property. However, if it exceeds 10%, the devitrification resistance is deteriorated, the yield point of the glass is increased, and strong coloring is caused. Become. Therefore, the content of TiO ₂ is limited to less than 0-10%. The content of the preferred TiO ₂ is in the range 0 to 8%. Further, if the total amount of TiO ₂ and WO ₃ is 5% or less, the desired high dispersion property cannot be obtained, and
If it exceeds 300, the devitrification resistance will deteriorate and the glass will be strongly colored. Therefore, the total amount of TiO ₂ and WO ₃ is limited to a range exceeding 5% and 22% or less. Preferred TiO
The total amount of ₂ and WO ₃ is in the range of 6-20%.

By adding Li ₂ O, Na ₂ O and K ₂ O in appropriate amounts, the effect of improving the devitrification resistance of the glass is very large, and the effect of lowering the glass yield point (Ts) is also improved. It is a very large component. Therefore, these 1
It is necessary that the total amount of the species or two or more species is 6% or more. However, the total amount of one or more of these is 20%
If it exceeds 300, the devitrification resistance will deteriorate. Therefore, (Li ₂ O
+ Na ₂ O + K ₂ O), the total amount of one or more of Li ₂ O, Na ₂ O and K ₂ O is limited to the range of 6 to 20%, preferably 8 to 17% Range.
However, Li ₂ O is 5%, Na ₂ O is 18%, K ₂ O is 1%.
If each exceeds 3%, the devitrification resistance of the glass deteriorates. Therefore, Li ₂ O is limited to a range of 0 to 5%, Na ₂ O is limited to a range of 0 to 18%, and K ₂ O is limited to a range of 0 to 13%. Preferably, Li ₂ O in the range of 0~3%, Na ₂ O in the range of 0~16%, K ₂ O is in the range 0-9%.

Optional components CaO, SrO and BaO
Is a component having a large effect of lowering the liquidus temperature of the glass by adding an appropriate amount and increasing the stability. However, if CaO exceeds 5%, SrO exceeds 5%, and BaO exceeds 10%, the intended high refractive index and high dispersion characteristics cannot be obtained,
In addition, the devitrification resistance also deteriorates. Therefore, the contents of CaO, SrO and BaO are respectively in the range of 0 to 5%, and 0 to 5%.
And the range of 0 to 10%. Preferably, CaO is in the range of 0-3% and SrO is 0-3%.
And BaO is in the range of 0 to 8%.

GeO ₂ , an optional component, is a component having a very large effect of increasing the stability of glass. However, 10
%, The desired high refractive index and high dispersion properties cannot be obtained, and the yield point of the glass also increases. Therefore GeO ₂ is limited to a range of 0%. Preferably, it is in the range of 0 to 8%.

The optional components ZnO and Ta ₂ O ₅
The refractive index can be adjusted by adding a small amount without deteriorating the devitrification resistance. However, ZnO exceeds 4% and Ta
_{When 2} O ₅ exceeds 6%, the devitrification resistance of the glass deteriorates. Therefore the content of ZnO in the range of 0~4%, Ta ₂ O
The content of ₅ is each limited to the range of 0 to 6%. Preferably in the range ZnO is 0~2%, Ta ₂ O ₅ is 0
４4%.

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. Further, SiO ₂ , La ₂ O ₃ , Y ₂ O ₃ ,
Gd ₂ O ₃ , Cs ₂ O, ZrO ₂ , Al ₂ O ₃ , MgO
And the like can be added as long as the object of the present invention is not impaired.

As raw materials for the optical glass having a low melting point of the present invention, orthophosphoric acid (H ₃ PO ₄ ), metaphosphate, diphosphorus pentoxide and the like are used for P ₂ O ₅ , and carbonates are used for other components. Nitrate, oxide, and the like can be used as appropriate.
These raw materials are weighed to a desired ratio and mixed to prepare a blended raw material, which is put into a melting furnace heated to 1000 ° C to 1200 ° C, melted, clarified, stirred, homogenized, and then cast into a mold. By slow cooling, 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 above-mentioned 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 further preferable optical product is an aspheric lens obtained by aspherical precision press of the low melting point optical glass of the present invention. The precision press can be performed using, for example, a press device as shown in FIG. FIG.
Is a quartz tube 11 having a molding die composed of an upper mold 1, a lower mold 2 and a guide mold 3 placed on a support 10 provided on a support rod 9 and a heater 12 wound around the outer periphery thereof. It is provided inside. The molded glass block 4 made of the low melting point optical glass of the present invention is disposed between the lower mold 2 and the upper mold 1. The molded glass lump 4 can be, 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 placing the glass lump 4 between the lower mold 2 and the upper mold 1, 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 set to a temperature at which the viscosity of the molded glass block 4 becomes suitable for precision press, for example, about ^107.6 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 can be in the range of 50 to 100 kg / cm ² , and the time can be 10 to 120 seconds. After pressing, the optical product of the present invention can be obtained by gradually cooling to a glass transition temperature, then rapidly cooling to room temperature, and taking out a molded product from a mold.

[0023]

The present invention will be further described below with reference to examples. Examples 1 to 12 According to the formulation (% by weight) shown in Table 1, by a conventional method,
The low melting point optical glass of the present invention (Examples 1 to 12) was prepared. 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 cast into a mold and slowly cooled to obtain a low melting point optical glass of the present invention. Table 1 shows the optical performance of the obtained glass. In the table, the refractive index nd and Abbe number νd are:
hr. The glass yield point (Ts) is the result when the temperature is raised at 8 ° C./min using a thermal expansion measuring device. The liquidus temperature (LT) is 400 ° C. to 105 ° C.
Hold in a devitrification test furnace with a temperature gradient of 0 ° C. for 30 minutes, observe the presence or absence of crystals with a microscope with a magnification of 80, and observe the devitrification near the softening point visually at the same time as measuring the liquidus temperature. This is the result.

[0024]

[Table 1]

Comparative Examples 1 to 3 Examples 9 and 12 described in JP-B-55-37500
Using the glasses Nos. 14 and 14 as Comparative Examples 1 to 3, the refractive index, Abbe number, liquidus temperature, and glass yield point (Ts) were measured.
Table 2 shows the results. This comparative glass uses Nb ₂ O ₅ and TiO ₂ as components having high refraction and high dispersion characteristics and does not use WO ₃ , so that it has poor devitrification resistance and a glass deformation point of 580 ° C. or higher. It turns out that it is not practical as a forming glass.

Comparative Examples 4 to 7 The glasses of Comparative Examples 4 to 7 were prepared as described in JP-B-56-400, respectively.
These are the glasses of Examples 1, 4, 7, and 14 described in JP-A-94. Table 2 shows the measurement results of the refractive index, Abbe number, liquidus temperature (LT), and glass yield point (Ts) of these glasses. Since these comparative glasses use only P ₂ O ₅ as a glass-forming oxide, they have poor devitrification resistance and a high glass yield point (Ts). K ₂ O is the most effective alkali metal oxide for lowering the yield point of glass.
Since only glass is used, the glass yield point is high, and it is understood that it is not practical as a glass for precision press molding.

[0027]

[Table 2]

Comparative Examples 8 to 14 The glasses of Comparative Examples 8 to 14 are the glasses of Examples 1, 2, 3, 4, 5, 6, and 8 described in JP-A-5-51233. Table 3 shows the results of measuring the refractive index, Abbe number, and glass yield point (Ts) of these glasses. These glasses have a liquidus temperature of 1000 even if the glass is devitrified during the melting of the glass or the glass is cast after melting.
It is understood that none of them is practical because the glass is devitrified when held at a temperature close to the softening point for 30 minutes.

[0029]

[Table 3]

Compared with the glasses of the examples, the glasses of the present invention of Examples 1 to 12 shown in Table 1 are low-melting optical glasses having a high refractive index and a high dispersion. Further, the glasses of Examples 1 to 12 of the present invention have a glass deformation point (Ts) of 570 ° C. or less, a liquidus temperature (LT) of all glasses of 900 ° C. or less, and a temperature of 30 ° C. near the softening point. The glass did not devitrify when held for minutes. In particular, Japanese Patent Publication No. 55-3
Compared to the glass described in Japanese Patent No. 7500, the glass of the present invention further contains a predetermined amount of WO ₃ in terms of composition, but is physically characterized by the liquidus temperature (LT) of the glass of the present invention. ) Was 900 ° C. or less. Also,
In Japanese Patent Publication 56-40094, a glass are also described containing WO _3, as shown as Comparative Example 7, merely the addition of WO _3, glass liquidus temperature (L.T ) Cannot be reduced. That is, it is understood that the low melting point optical glass having the above-mentioned excellent properties can be obtained for the first time by setting each component constituting the glass and the content range thereof to the range of the present invention. From the results of the above examples, unlike the glasses listed in the comparative examples,
It can be seen that each of the glasses of the present invention has stability such that lenses can be mass-produced by precision pressing.

Example 13 Using the glass of Example 2, an aspherical lens was obtained by performing an aspherical precision press using the press apparatus shown in FIG. After the glass of Example 4 having a spherical shape having a diameter of 2 to 20 mm was placed between the lower mold 2 and the upper mold 1, the quartz tube 11 was heated by energizing the heater 12 with a nitrogen atmosphere in the quartz tube 11. . After setting the temperature in the molding mold to 570 ° C. at which the viscosity of the glass mass to be molded becomes about 10 ^7.6 poise, while maintaining this temperature, the push rod 13 is lowered to push the upper mold 1 from above to thereby form the inside of the molding mold. Was pressed.
The pressing pressure was 80 kg / cm ² , and the pressing time was 30 seconds. After pressing, the pressure of the press is released, and the glass molded body formed by the aspherical press molding is gradually cooled to a glass transition temperature of 495 ° C. while being kept in contact with the lower mold 2 and the upper mold 1, and then to around room temperature. The glass that was quenched and formed into an aspherical surface was removed from the mold. The obtained aspherical lens was an extremely accurate lens.

[0032]

According to the present invention, a low melting point optical material having a high refractive index and a high dispersion property, a glass having a deformation point of 570 ° C. or lower, having devitrification resistance, being stable, and having excellent moldability. Glass can be provided. 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. Further, optical products such as aspherical 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.

Claims (7)

(57) [Claims] 1. The following components are represented by the following contents (in% by weight).
(Excluding GeO ₂ and Al ₂ O ₃ ). _{P 2 O 5 16~38% B 2} O 3 1~20% Nb 2 O 5 14~44% PbO 7~26% WO 3 below 1~20% TiO ₂ 0~10% (however, TiO ₂ + WO ₃ 5 %, greater or less _{22%) Li 2 O 0~5%} Na 2 O 0~18% K 2 O 0~13% ( _{however, Li 2 O + Na 2 O} + K 2 O 6~20%) 2. The low melting point optical glass according to claim 1, wherein the total content of each component is 80% or more. 3. 0-5% of CaO, 0-5% of SrO,
The low melting point optical glass according to claim 1, further comprising 0 to 10% of BaO and 0 to 4% of ZnO. 4. An amount of 0 to 6% of Ta ₂ O ₅ and 0 to 2 of As ₂ O ₃ .
%, Low melting optical glass according to any one of claims 1 to 3 containing Sb ₂ O ₃ 0 to 2% more. 5. The method according to claim 1, wherein the refractive index is in the range of 1.73 to 1.84, the dispersion is in the range of 29 to 23, and the glass deformation point (Ts) is 570 ° C. or less. 2. The low melting point optical glass according to claim 1. 6. An optical product obtained by precision-pressing the low-melting-point optical glass according to claim 1. 7. An aspherical lens obtained by subjecting the low-melting-point optical glass according to claim 1 to aspherical precision press.