JPH11139844A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable optical glass having an optical constant in a prescribed range and satisfactory chemical durability, excellent in devitrification resistance and meltability and without contg. components of expensive starting materials such as Gd2 O3 and Ta2 O5 or without requiring the components as essential components. SOLUTION: The optical glass consists of a compsn. contg., by weight, >5% to 20% SiO2 , 35-55% B2 O3 , 0 to <10% Al2 O3 , 10-30% La2 O3 , 0.5-15% Y2 O3 , 10-30% CaO, >0 to <0.5% Li2 O, 0-5% MgO< 0-5% SrO, 0-15% BaO, 0-15% ZnO, 0-3% TiO2 , 0-5% ZrO2 , 0-5% Nb2 O5 , 0-5% Ta2 O5 , 0-5% WO3 and 0-1% Sb2 O3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical glass having an optical constant having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 55 or more.

[0002]

2. Description of the Related Art Conventionally, as optical glasses having an optical constant within the above range, for example, SiO ₂ , B ₂ O ₃ and BaO
Glasses having as a basic component are known. Glass of this composition has excellent stability when melted, but has very poor chemical durability, and burns on the glass surface during the glass polishing and cleaning processes and the long-term use process as a lens. In particular, special attention was required when processing and using the above-mentioned conventional glass. In addition, the above conventional glass tends to have a large specific gravity because it contains a relatively large amount of BaO component, and furthermore, when the prepared raw material is melted, the SiO ₂ component is easily separated on the surface of the melt, and the homogeneity is high. There is a problem that it is difficult to obtain a suitable glass.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art, to provide an optical constant within the above-mentioned predetermined range, good chemical durability, and to withstand loss. It is an object of the present invention to provide a stable optical glass which is excellent in permeability and meltability and does not contain expensive components such as Gd ₂ O ₃ and Ta ₂ O ₅ or does not contain them as essential components.

[0004]

Means for Solving the Problems The inventor of the present invention has conducted intensive tests and researches to solve the above-mentioned problems, and as a result, has obtained a SiO ₂ —B ₂ O ₃ —CaO—La ₂ O ₃ glass having a specific composition range. L
It has been found that the above object can be achieved by adding i ₂ O and Y ₂ O ₃ as essential components, and the present invention has been accomplished.

[0005] That is, the feature of the optical glass of the present invention for achieving the above object is that, as described in claim 1, the content of B ₂ O ₃ 3 is more than 5% and up to 20% by weight of SiO _2.
5 to 55%, Al ₂ O ₃ 0 to less than 10%, La ₂ O ₃ 1
_{0~30%, Y 2 O 3 0.5~15} %, CaO 10~
30%, Li ₂ O 0% to less than 0.5%, Mg
O 0-5%, SrO 0-5%, BaO 0-15
%, ZnO 0 to 15% TiO ₂ 0 to 3%, ZrO _{2
0~5%, Nb 2 O 5 0~5} %, Ta 2 O 5 0~5%,
WO ₃ is in place consisting of 0-5% and Sb ₂ O ₃ 0~1% of the composition.

Further, as described in claim 2, the weight%
And SiO ₂ 6 to 15%, B ₂ O ₃ 40 to 50%, A
_{l 2 O 3 0.3~5%, La} 2 O 3 10~25%, Y 2
O ₃ 1 to 12%, provided that La ₂ O ₃ + Y ₂ O ₃ 15 to
30%, CaO 18-25%, Li ₂ O more than 0% and less than 0.5%, MgO 0-5%, SrO 0-5
%, BaO 0-10%, ZnO 0-10% ZrO _{2
0~5%, Ta 2 O 5 0~5} % and Sb ₂ O ₃ 0 to
0.5% of TiO ₂ , Nb ₂ O ₅ and W
O ₃ is not contained.

[0007] Further, as described in claim 3, the weight%
And SiO ₂ 6 to 15%, B ₂ O ₃ 40 to 50%, provided that SiO ₂ + B ₂ O _{3 is} 50% or more, and Al ₂ O ₃ .
_{3~5%, La 2 O 3 10~25} %, Y 2 O 3 1~12
%, But La ₂ O ₃ + Y ₂ O ₃ 15 to 30%, CaO
18 to 25%, up to Li ₂ O less than 0%, greater 0.5%, 0~5% MgO, SrO 0~5%, BaO 0
-10%, ZnO 0-10%, ZrO ₂ 0-5%, T
a ₂ O ₅ consists 0-5% and Sb ₂ O ₃ 0~0.5% of the composition, there is to not containing TiO _2, Nb ₂ O ₅ and WO _3.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why each component is limited to the above-mentioned composition range in the optical glass of the present invention will be described below. S
The iO ₂ and B ₂ O ₃ components are glass forming oxides,
In the present invention, it is effective to widen the vitrification range and give the glass an appropriate viscosity. If the content of the SiO ₂ component is 5% or less, the above effect is insufficient, and 2%
If the content exceeds 0%, the meltability of the mixed raw material deteriorates, and an unmelted material is easily generated. The amount of the B ₂ O ₃ component is 35%.
% Or more than 55%, it becomes difficult to obtain a glass having a desired refractive index. In particular, in order to obtain glass with good homogeneity, it is preferable that the amount of the SiO ₂ component is 6 to 15% and the amount of the B ₂ O ₃ component is 40 to 50%. further,
In order to obtain more stable glass, the total amount of the SiO ₂ component and the B ₂ O ₃ component is more preferably set to 50% or more.

The Al ₂ O ₃ component is effective for improving the chemical durability of the glass, adjusting the viscosity, and stabilizing the glass against devitrification. However, when the amount is 10% or more, the devitrification is rather increased, which is not preferable. A more preferred amount is 0.3
~ 5%.

The La ₂ O ₃ component not only improves the chemical durability and devitrification resistance of the glass, but also increases the refractive index without excessively increasing the dispersion, thereby obtaining a stable glass having a high refractive index. It is an effective ingredient. That amount is 10%
If it is less than 30, the glass has insufficient chemical durability and devitrification resistance, and if it exceeds 30%, a desired refractive index cannot be obtained. In order to obtain a homogeneous glass having a desired optical constant and no devitrification, the content of the La ₂ O ₃ component is 10 to 25%.
More preferably, it is within the range.

Like the La ₂ O ₃ component, the Y ₂ O ₃ component improves the chemical durability and devitrification resistance of the glass, increases the refractive index without excessively increasing the dispersion, and further increases the specific gravity. It is an effective ingredient for reducing the size. 0.5% of that amount
If it is less than 15%, the above effect is not sufficient, and if it exceeds 15%, the temperature at which crystals precipitate is rather increased, and the glass tends to be devitrified. A more preferred range of the amount of the Y ₂ O ₃ component is 1 to 12%. Further, in the present invention, in order to obtain more stable glass, the La ₂ O ₃ component and the Y
It is preferable that the total amount of the ₂ O ₃ component be 15 to 30%.

The CaO component is effective in improving the chemical durability, devitrification resistance, and the melting property of the glass raw material of the glass. If the amount of the CaO component is less than 10%, the above effect is not sufficient, and it is difficult to obtain a desired optical constant. On the other hand, if the amount exceeds 30%, the tendency of devitrification increases, which is not preferable. A more preferable amount of the CaO component is 18 to 25%.
It is.

In the present invention, the Li ₂ O component is an essential component effective for accelerating the melting of the glass raw material. However, in order to obtain the above-mentioned effect, the amount thereof is less than 0.5%. . Further, a part of the Li ₂ O component is changed to Na ₂ O and K ₂ O.
It is possible to replace one or both of the components.

Each component of MgO, SrO, BaO and ZnO is effective for adjusting the refractive index and Abbe number of the glass, improving the melting property of the glass raw material and improving the devitrification resistance. To 5% each, and the BaO and ZnO components to 15% each. It is more preferable that the amounts of the BaO and ZnO components are each up to 10%.

The glass of the present invention has a refractive index and an Abbe number.
TiO2 for conditioning or improving glass stability_Two, Z
rO_Two , Nb_TwoO_Five, Ta_TwoO_FiveAnd WO_ThreeEach component of
The amount of TiO 2_TwoIngredient is 3%
Up to ZrO_Two, Nb_TwoO_Five, Ta _TwoO_FiveAnd WO_ThreeEach of
In each case up to 5% is sufficient. However, TiO
_Two, Nb_TwoO_FiveAnd WO_Three The component is
They tend to lower the light transmittance of the glass,
It is more preferable that no component is contained.

The Sb ₂ O ₃ component can be arbitrarily added as a fining agent at the time of melting the glass, but the amount of 1% or less is sufficient, and a more appropriate amount is 0.5% or less. Further, in addition to the above components, components such as metal element fluorides and P ₂ O ₅ contained in each of the above metal oxide components may be added to the glass of the present invention in an amount of up to 5%. Absent.

[0017]

Next, Examples (No. 1 to No. 4) of the optical glass according to the present invention and Comparative Examples (No. A) of the conventional glass will be described with reference to the refractive index (nd) and Abbe number of these glasses. (Νd), devitrification temperature (° C.), specific gravity, and the weight ratio of Y ₂ O ₃ to La ₂ O ₃ are shown in Table 1, and are shown in Examples (No. 1 to No. 4) and Comparative Example (No. A). FIG. 1 shows the relationship between the content of the Y ₂ O ₃ component of the glass and the devitrification temperature (° C.). The above-mentioned devitrification temperature is obtained by placing each crushed piece of glass on a small hole provided in a platinum plate, melting it in a temperature gradient furnace and holding it for 30 minutes, taking it out of the furnace, and observing the state of crystal generation with a microscope. It shows the results obtained by observation.
Further, another embodiment of the optical glass according to the present invention (No.
5-No. 41) together with the refractive index (nd) and Abbe number (νd) of these glasses are shown in Tables 2, 3, 4 and 5.
And Table 6.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

[Table 6]

As shown in Table 1 and FIG. 1, the glasses of the examples of the present invention have a lower devitrification temperature, are more excellent in devitrification resistance, and have a lower specific gravity than the glasses of the comparative examples. Further, the glasses of the above examples are all excellent in melting property,
A homogeneous glass without bubbles and striae is obtained, and the chemical durability is also good. Similarly, the glasses of Examples of the present invention shown in Tables 2 to 6 are also excellent in devitrification resistance, melting property and chemical durability, and have low specific gravity. The glasses of the examples of Tables 1 to 6 according to the present invention were prepared by weighing and mixing ordinary optical glass materials such as oxides, carbonates, hydroxides, nitrates and fluorides, and using a platinum crucible or the like. About 120
It can be easily manufactured by melting, fining and stirring at 0 ° C. to 1400 ° C. for about 2 to 4 hours, then casting into a preheated mold and slowly cooling.

[0025]

As described above, the optical glass of the present invention has a specific composition range of SiO ₂ —B ₂ O ₃ —CaO—La ₂
It is a glass obtained by adding Li ₂ O and Y ₂ O ₃ as essential components to an O ₃ -based glass, and has a refractive index (nd) of 1.60 to
1.68, it is possible to obtain a stable and homogeneous optical glass having an optical constant of Abbe number (νd) of 55 or more, excellent in devitrification resistance and melting property, and having good chemical durability. it can. Furthermore, the optical glass of the present invention is useful in that it does not contain a Gd ₂ O ₃ component, which is expensive in raw materials, does not contain a Ta ₂ O ₅ component as an essential component, and can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the content of a Y ₂ O ₃ component and the devitrification temperature (° C.).

Claims (3)

[Claims] 1. A weight%, up to 20% greater than the _{SiO 2 5%, B 2 O} 3 35~55%, Al 2 O 3 less than _{0~10%, La 2 O 3 10~30} %, Y 2 O ₃ 0.5-15
%, CaO 10 to 30%, and Li ₂ O exceeding 0%.
Until less than 5%, MgO 0-5%, SrO 0-5%,
BaO 0-15%, ZnO 0-15% TiO ₂ 0
_{~3%, ZrO 2 0~5%,} Nb 2 O 5 0~5%, T
_{a 2 O 5 0~5%, WO} 3 0~5% and Sb ₂ O ₃ 0
An optical glass comprising a composition of about 1%. 2. The optical glass according to claim 1, wherein SiO _{2 is} 6 to 15% and B ₂ O _{3 is} 40 to 50% by weight.
_{%, Al 2 O 3 0.3~5%} , La 2 O 3 10~25
_{%, Y 2 O 3 1~12%} , _{however, La 2 O 3 + Y 2} O 3
15~30%, CaO 18~25%, Li 2 O 0%
Over 0 to less than 0.5%, MgO 0-5%, SrO
0-5%, BaO 0-10%, ZnO 0-10% Z
rO ₂ 0-5%, Ta ₂ O ₅ 0-5% and Sb ₂ O ₃
Consists from 0 to 0.5% of the composition, optical glass characterized in that it does not contain TiO _2, Nb ₂ O ₅ and WO _3. 3. The optical glass according to claim 1, wherein 6 to 15% of SiO _{2 and} 40 to 50% of B ₂ O ₃ by weight.
%, But at least 50% of SiO ₂ + B ₂ O ₃ , Al ₂ O _{3
0.3~5%, La 2 O 3 10~25} %, Y 2 O 3 1
１２12%, provided that La ₂ O ₃ + Y ₂ O ₃ 15-30%,
CaO 18-25%, Li ₂ O more than 0% and 0.5%
To less than 0 to 5% of MgO, 0 to 5% of SrO, Ba
O 0-10%, ZnO 0-10% ZrO ₂ 0-5
%, Ta ₂ O ₅ 0~5% and Sb ₂ O ₃ 0~0.5%
An optical glass having the following composition and containing no TiO ₂ , Nb ₂ O ₅ and WO ₃ .