JP2000001329A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical glass having such optical constants as a refractive index (nd) of 1.67 to <1.74 and an Abbe's number (νd) of 35 to <45, excellent in devitrification resistance and chemical durability, hardly causing defects such as crazing and shrinkage due to thermal shrinking in a formed article at the time of cooling after press forming and excellent in profitableness because of a low material cost. SOLUTION: The optical glass has a compsn. consisting of, by weight, 20.5-35% B2O3, 17.5-30% SiO2 (B2O3+SiO2=42-60%), 3.5-7% Li2O, 0-5% Na2O, 0-5% K2O, 0-10% MgO, 9-23% CaO, 0-4% BaO, 0-10% ZnO, >15 to 30% La2O3, 0-15% Gd2O3, 4-14% TiO2, 1-10% ZrO2, 1-20% Nb2O5, 0-5% Al2O3 and 0-1% Sb2O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the present invention having a refractive index (nd) of 1.67 to less than 1.74 and an Abbe number (νd) of 35 to 4.
It has an optical constant in the range of less than 5, is excellent in devitrification resistance and chemical durability, and can be used for mold press molding which can directly obtain an optical element without requiring grinding or polishing after press molding. B ₂ O _{3 with} a new specific composition range suitable for
—SiO ₂ —Li ₂ O—CaO—La ₂ O ₃ —TiO ₂ —Z
The present invention relates to an rO ₂ —Nb ₂ O ₅ based optical glass.

[0002]

2. Description of the Related Art Conventionally, as a glass having an optical constant close to the above range, Japanese Patent Publication No. 53-42327 discloses S-glass.
_{iO 2 -CaO-R 2 O-} TiO 2 -Nb but ₂ O ₅ based glass for the spectacle lens is disclosed, the glass is not suitable for mass production because of poor resistance to devitrification. Also, Japanese Patent Publication No. 5-37935 discloses B ₂ O ₃ —SiO ₂ —Li ₂
Although _{O-CaO-La 2 O 3} -TiO 2 -ZrO 2 -Nb 2 O 5 based glass is disclosed, the glass, after poor devitrification resistance and chemical durability, the average linear thermal expansion Because the coefficient is large, when cooling the glass molded product obtained by press-molding the heat-softened glass, the molded product is broken by thermal shrinkage, or the phenomenon that the molded surface is dented by being pulled by the thermal shrinkage inside the glass, so-called There is a problem that sinks occur. Japanese Patent Application Laid-Open No. 57-511149 discloses S
Although an iO ₂ -B ₂ O ₃ -R ₂ O-CaO-TiO ₂ glass is disclosed, this glass has excellent chemical durability, but has poor devitrification resistance, and has an average The linear thermal expansion coefficient cannot be said to be sufficiently small, and the above-mentioned problems of cracks and sink marks have not been solved.

Japanese Patent Application Laid-Open No. 60-221338 discloses B ₂ O ₃ -La ₂ O ₃ -Y ₂ O ₃ -bivalent metal oxide-Li
_A 2O-based glass is disclosed. This glass is provided with a low transition temperature characteristic for the purpose of extending the life of a mold, and Gd ₂ O ₃ and Ta ₂ O _5, which have high raw material costs, are used in order to make the glass excellent in raw material economics. Although the optional component, for Gd ₂ O ₃ and Ta ₂ O ₅ and likewise material cost contains high Y ₂ O ₃ as an essential component, said that the improvement of the raw material economy have been made sufficiently hard. Furthermore, the publication does not describe anything about the average coefficient of linear thermal expansion, and does not show means for solving the above-mentioned problems of cracks and sink marks. Further, in _{JP-A-54-161619, SiO 2 -B 2 O 3} -MgO and / or CaO
-TiO ₂ -La ₂ O ₃ but -BaO and / or SrO-based glass for the spectacle lens is disclosed, the glass, after the coloring property is a strong disadvantage, the refractive index (nd) of 1.77～ It is 1.81 which is considerably higher than the range of the refractive index aimed at by the present invention.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to comprehensively solve the above-mentioned problems of the prior art, have an optical constant in the desired range, and have excellent devitrification resistance and chemical durability. Another object of the present invention is to provide an optical glass which is free from defects such as cracks and sink marks due to heat shrinkage in a molded product at the time of cooling after press molding, is low in raw material cost, and is excellent in economic efficiency.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies and studies to achieve the above object, and as a result, have found that the content of glass-forming oxides in a specific composition range is limited to a specific range.
₂ O ₃ —SiO ₂ —Li ₂ O—CaO—La ₂ O ₃ —TiO ₂
In -ZrO ₂ -Nb ₂ O ₅ based glass, has optical constants of the desired range, the devitrification resistance and excellent chemical durability, upon cooling the glass molded article obtained by press molding, heat molded products It was found that a glass having a viscosity suitable for press molding was obtained without causing cracks or sink marks due to shrinkage,
The present invention has been made.

That is, the feature of the optical glass according to claim 1 of the present invention for achieving the above object is as follows:
_{B 2 O 3 20.5~35%, SiO} 2 17.5~30
%, _{However, B 2 O 3 + SiO 2} 42~60%, Li 2 O
_{3.5~7%, Na 2 O0~5%,} K 2 O 0~5%,
MgO 0-10%, CaO 9-23%, BaO 0
４4%, ZnO 0１０10%, La ₂ O ₃ 15 <〜30
_{%, Gd 2 O 3 0~15%} , TiO 2 4~14%, Z
rO ₂ 1-10%, Nb ₂ O ₅ 1-20%, Al ₂ O ₃
There is to consisting of 0-5% and Sb ₂ O ₃ 0~1% of the composition.

In order to achieve the above object, the optical glass according to the second aspect of the present invention is characterized in that, in terms of% by weight, B _{2
O 3 21~35%, SiO 2 18~30} %, however,
_{B 2 O 3 + SiO 2 42~60} %, Li 2 O 3.5~7
_{%, Na 2 O 0~5%,} K 2 O 0~5%, MgO 0
-10%, CaO 10-23%, BaO 0-4%,
_{0~10% ZnO, La 2 O 3} 16~28%, Gd 2
_{O 3 0~15%, TiO 2 4~13} %, ZrO 2 1
_{~10%, Nb 2 O 5 1~20} %, Al 2 O 3 0~5%
And Sb ₂ O ₃ consists of 0 to 1% of the composition, the refractive index (n
d) is 1.67 to less than 1.74, Abbe number (νd) is 3
It has an optical constant in the range of 5 to less than 45 and has an average linear thermal expansion coefficient (α × 10 ⁻⁷ / ° C.) of less than 90 × 10 ⁻⁷ / ° C.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the composition ranges of the respective components of the optical glass according to the present invention as described above are as follows. B ₂ O ₃ component is a glass forming oxide is a component necessary for stably introducing a relatively large amount of La ₂ O ₃ component to increase the refractive index of the glass, B ₂ O ₃ component If the amount is less than 20.5%, the glass tends to be devitrified and the glass becomes unstable.
The optical constants targeted by the present invention cannot be obtained. B ₂ O ₃
A particularly preferred range for the amounts of the components is 21-35%.

The SiO ₂ component is a glass-forming oxide and has the effect of increasing the viscosity of glass and facilitating press molding. However, if the amount is less than 17.5%, the above effects cannot be sufficiently obtained. In addition, press molding becomes difficult, and the chemical durability and devitrification resistance of the glass deteriorate. In addition, 30%
If it exceeds, the melting property of the glass becomes worse and the tendency of devitrification increases. A particularly preferred range for the amount of the SiO ₂ component is 18-30%. In addition, B ₂ O ₃ and SiO ₂
If the total amount of the components is less than 42%, the devitrification resistance and chemical durability of the glass will deteriorate, and the average linear thermal expansion coefficient of the glass will increase. As a result, cracks and sink marks tend to occur in the molded product. If the total amount of these components exceeds 60%, the optical constants targeted by the present invention cannot be obtained.

When the glass is melted, the Li ₂ O component becomes SiO _2.
It has the effect of accelerating the melting of the raw material and reducing the tendency to devitrify. To obtain the above effect, it is necessary to contain 3.5% or more, but if it exceeds 7%, the tendency to devitrify increases, Further, the chemical durability of the glass deteriorates.

The CaO component must be contained in an amount of 9% or more to suppress the tendency to devitrify and obtain a stable glass.
If it exceeds 23%, the tendency to devitrify will be rather increased. Ca
A particularly preferred range of the amount of the O component is 10 to 23%.

The La ₂ O ₃ component is a component having an effect of increasing the refractive index of the glass. If the content is less than 15%, the optical constant targeted by the present invention cannot be obtained. The tendency to devitrification increases. A particularly preferred range of amounts of la ₂ O ₃ component is 16 to 28%.

The TiO ₂ component has an effect of increasing the refractive index while maintaining the stability of the glass. However, if the amount is less than 4%, the desired optical constant targeted by the present invention cannot be obtained. On the other hand, if it exceeds 14%, the devitrification tendency of the glass increases, and the coloring becomes remarkable. The amount of the TiO ₂ component is 13
% Is particularly preferred.

The ZrO ₂ component increases the refractive index of the glass,
In addition, the coexistence with the Nb ₂ O ₅ component has the effect of improving the chemical durability. However, if the amount is less than 1%, the effects are not sufficient. And the tendency to devitrify increases.

The Nb ₂ O ₅ component has the effect of increasing the chemical durability of the glass when it coexists with the above-mentioned ZrO ₂ component, and is an indispensable component in the glass of the present invention. In order to obtain the above-mentioned coexistence effect and to obtain the desired optical constant targeted by the present invention, it is necessary to contain 1% or more, but the refractive index targeted by the present invention is maintained. And, in order to suppress an increase in raw material cost, the amount should be up to 20%.

The following components can be optionally added to the glass of the present invention as needed. Each of the Na ₂ O and K ₂ O components can be added up to 5% in order to improve the melting property of the glass within a range in which the desired refractive index targeted by the present invention can be maintained. MgO, BaO and ZnO
Any of the components can be added up to 10%, 4% and 10%, respectively, for adjusting the optical constants within a range that does not deteriorate the devitrification resistance and chemical durability of the glass. Gd ₂
The O ₃ component can be added for adjusting the optical constants or improving the devitrification resistance of the glass. However, the amount should be up to 15% in order to suppress an increase in the raw material cost. preferable. The Al ₂ O ₃ component improves the chemical durability of the glass, increases the viscosity and facilitates press molding, but if the amount exceeds 5%, the tendency of the glass to devitrify increases. The Sb ₂ O ₃ component has an effect of promoting defoaming and fining at the time of glass melting, but an amount of up to 1% is sufficient.

[0017]

Next, examples of the optical glass of the present invention will be described. Examples of the optical glass of the present invention (No.
1 to No. 10), the conventional B ₂ O ₃ —SiO ₂ —Li _{2
O-CaO-La 2 O 3} -TiO 2 -ZrO 2 -Nb 2 O Comparative Example ₅ based glass (No. A and No.B) and the conventional _{SiO 2 -B 2 O 3 -R 2} O- Comparative examples (No. C and No. D) of CaO—TiO ₂ glasses are shown in Tables 1 and 2 together with the refractive index (nd), Abbe number (νd) and devitrification resistance test results of these glasses. Was. Table 1
And in the devitrification resistance test in Table 2, a glass material batch prepared in advance was charged into a 300 cc platinum crucible,
12 depending on the degree of melting of each glass sample in an electric furnace
After melting at 00 to 1300 ° C for 2 hours, the temperature was lowered, each sample was kept at 900 ° C and 850 ° C for 1 hour, respectively, taken out of the furnace, and observed for devitrification with a microscope. , A glass sample in which no devitrification was observed is indicated by a circle, and a glass sample in which devitrification was observed is indicated by a cross.

In the above embodiment (No. 1 to No. 1)
Table 3 shows the acid resistance (SR value) of the glasses of Comparative Example No. 0) and Comparative Examples (No. A and No. B). Note that S
The R value is determined by the International Organization for Standardization ISO 8424: 1996
It shows the results obtained by measuring according to the measuring method of (E). Here, the SR value is a value that is graded according to the time (h) required for a glass sample to undergo erosion of 0.1 μm in a predetermined acid treatment solution. S in Table 3
R values = 5, 51 and 53 indicate that the time (h) required to undergo 0.1 μm erosion using acetate buffer at pH = 4.6 is h> 10 and h = 1-10, respectively. And h
<0.1. Therefore, the smaller the SR value, the higher the acid resistance of the glass and the better the chemical durability.

Further, the above embodiments (No. 1 to No. 3)
And 1 of the glass of the comparative examples (No. A to No. D).
Table 4 shows the average linear thermal expansion coefficient (α × 10 ⁻⁷ / ° C.) in the temperature range of 00 to 300 ° C.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

As can be seen from Tables 1 and 2, the glasses of Examples of the present invention each have an optical constant in a desired range, and have the results of the above-described devitrification resistance test.
No devitrification was observed, and the glass (No.
o. The devitrification resistance is superior to D). Further, as can be seen from Table 3 above, the glasses of the examples of the present invention were all the glasses of the comparative examples (No. A and No. B).
As compared with, the SR value is small, the acid resistance is high, and the chemical durability is excellent. Further, as seen in Table 4 above,
Each of the glasses (No. 1 to No. 3) of the examples of the present invention has an average linear thermal expansion coefficient (α × 10 ⁻⁷ /) which is larger than the glasses of the comparative examples (No. A to No. D). ℃)
It can be seen that the heat shrinkage of the glass after press-molding the heat-softened glass during cooling is smaller than that of the conventional glass of the comparative example. As described above, as can be seen from Tables 1 to 4, the glasses of the examples of the present invention have better devitrification resistance than the conventional glasses of the comparative examples, while maintaining excellent chemical durability, and Small average coefficient of linear thermal expansion (α × 10 ^-7 /
° C), which indicates that the disadvantages of the conventional glass of the comparative example are totally improved.

The glass of the above embodiment of the present invention was prepared by weighing and mixing ordinary optical glass materials such as oxides, carbonates, and nitrates, and using a platinum crucible or the like to mix the materials at about 1200 ° C.
It can be easily manufactured by melting, lighting, stirring and homogenizing at 1300 ° C. for about 3 to 4 hours, then casting into a preheated mold, and gradually cooling. In addition, all of the glasses of the above examples are excellent in meltability and can easily obtain a highly homogeneous glass without bubbles and striae, and have a moderately high viscosity. Can also be easily performed.

[0026]

As described above, the optical glass according to the present invention has a specific composition range of B ₂ O ₃ —SiO ₂ —Li ₂ O—CaO— in which the content of the glass-forming oxide is limited to a specific range.
Since it is a La ₂ O ₃ —TiO ₂ —ZrO ₂ —Nb ₂ O ₅ system glass, it has an optical constant in the desired range, is excellent in devitrification resistance and chemical durability, and has a moderately high viscosity. Press molding is easy, and the average coefficient of linear thermal expansion (α × 10 ⁻⁷ / ° C.) is small. No sink marks occur, and the yield of press molding can be improved. In addition, because of its excellent melting property, it is possible to easily produce a homogeneous glass without bubbles, striae, etc.
And high raw material prices component as ₂ O _3, PbO and As ₂ O ₃
Since it does not contain components that require high costs for waste treatment for environmental measures as described above, it is also advantageous in terms of manufacturing costs and waste treatment costs.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G062 AA04 BB05 DA04 DB01 DB02 DB03 DC04 DC05 DD01 DE01 DE02 DE03 DF01 EA03 EB01 EB02 EB03 EC01 EC02 EC03 ED01 ED02 ED03 EE03 EE04 EF01 EG01 EG02 EG03 FA01 FB03 FB03 FB01 FJ01 FK04 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 KK01 KK03 KK04 KK05 KK07 MM02 NN02 NN03

Claims (2)

[Claims] (1) B ₂ O ₃ 20.5-35% by weight, S
iO ₂ 17.5 to 30%, provided that B ₂ O ₃ + SiO _{2
42~60%, Li 2 O 3.5~7%} , Na 2 O 0~
_{5%, K 2 O 0~5%} , 0~10% MgO, CaO
9-23%, BaO 0-4%, ZnO 0-10
_{%, La 2 O 3 15 <} ~30%, Gd 2 O 3 0~15
_{%, TiO 2 4~14%, ZrO} 2 1~10%, Nb
_{2 O 5 1~20%, Al 2} O 3 0~5% and Sb ₂ O ₃
An optical glass comprising a composition of 0 to 1%. 2. A _{weight%, B 2 O 3 21~35%} , SiO
₂ 18 to 30%, provided that B ₂ O ₃ + SiO ₂ 42 to 6
_{0%, Li 2 O 3.5~7%} , Na 2 O0~5%, K 2
O 0-5%, MgO 0-10%, CaO 10-2
3%, BaO 0-4%, ZnO 0-10%, La _{2
O 3 16~28%, Gd 2 O} 3 0~15%, TiO 2
4-13%, ZrO ₂ 1-10%, Nb ₂ O ₅ 1-2
0%, Al ₂ O ₃ 0-5% and Sb ₂ O ₃ 0-1%, having a refractive index (nd) of 1.67-1.74 and an Abbe number (νd) of 35-45. And the average coefficient of linear thermal expansion (α × 10 ⁻⁷ / ° C.) is 90.
An optical glass characterized by being less than × 10 ⁻⁷ / ° C.