JP2000247678A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical glass which has a refractive index(nd) of 1.47-1.53, an Abbe's number(νd) of 60-68, low yield point(At) and excellent chemical durability. SOLUTION: The optical glass contains, by weight, 60-65% SiO2, 14-19% B2O3, 5-9% Al2O3, 2-6.5% Li2O, 4-7% Na2O, 2-6.5% K2O, 11-16% Li2O+Na2O+K2 O, >=0.05 and <1 TiO2 and 0-2% Sb2O3 and has optical constants such that the refractive index(nd) is in the range of 1.47-1.53 and the Abbe's number is in the range 60-68.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical glass, and more particularly to an optical glass suitable for mold press molding.

[0002]

2. Description of the Related Art Conventionally, mold press molding has been widely used as a useful processing method for optical glass. In particular, precision mold press molding has recently gained utility because it does not require grinding or polishing after press molding, and can directly obtain an optical element such as a lens and can simplify the manufacturing process. In such a mold press molding, when the molding temperature of the glass is high, the durability of the molding die is reduced, and the releasability of the glass from the mold is deteriorated by burning of the glass into the molding die. Therefore, it is desirable that the yield point (At) of the glass is as low as possible.

On the other hand, optical glasses used for lenses and the like are required to have various optical constants. Among them, a desired optical constant, specifically, a refractive index (nd) is required.
1.47 to 1.53, Abbe number (νd) 60 to 68
Are also required. As optical glasses having such an optical constant, various borosilicate crown-based or barium crown-based glasses are known,
For example, in the "Glass Composition Data Book, 1991 Edition (published by the Japan Glass Products Industries Association)", BK (Shotgrass-Werke, Inc.) type glass is used as a borosilicate crown glass, and barium crown glass is used as a barium crown glass. A glass of BaLK (trade name of Shotgrass-Werke) is described.

[0004]

However, these BK-type and BaLK-type glasses generally have a high yield point (At), and most of them exceed 550 ° C., and have high molding temperatures. There is a problem that the glass is unsuitable.

In order to solve the above problems, R ₂
Glasses containing O (alkali metal oxide) have been proposed. For example, Japanese Patent Application Laid-Open No. Hei 5-193977 discloses an optical glass in which R ₂ O (alkali metal oxide) is introduced into a SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ composition. Glass has the disadvantage of poor chemical durability, especially acid resistance.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a refractive index (n)
d) is 1.47 to 1.53, Abbe number (νd) is 60 to
Having an optical constant in the range of 68, a low yield point (At),
An object of the present invention is to provide an optical glass which has good releasability from a molding die and has high chemical durability, particularly excellent acid resistance.

[0007]

[Means for Solving the Problems] The above problems should be solved.
In addition, the present inventors have conducted intensive research and studies and found that
Specific composition ranges not specifically disclosed in the technology
Having, SiO_Two-B_TwoO _Three-Al_TwoO_Three-R_TwoO (alkali
TiO to metal oxide) based glass_TwoTo add the ingredients
As a result, an optical glass having characteristics that solve the above-mentioned problems is obtained.
And found that the present invention was achieved.

That is, the optical glass according to the first aspect of the present invention has a SiO ₂ content of 60 to 65% by weight and a B ₂ O ₃ content by weight%.
_{14~19%, Al 2 O 3 5~9} %, Li 2 O 2~6.
5%, Na ₂ O 4 to 7%, K ₂ O _{2 to} 6.5% However, Li ₂ O + Na ₂ O + K ₂ O 11 to 16%, T
iO less than ₂ from 0.05 to 1%, and containing the respective components of Sb ₂ O ₃ 0 to 2% range, the refractive index (nd) of 1.47 to 1.
53, characterized in that the Abbe number (νd) has an optical constant in the range of 60 to 68.

Further, the optical glass of the present invention according to claim 2 has a SiO ₂ content of 60 to 65% by weight and a B ₂ O ₃ 14 by weight%.
１９19%, provided that B ₂ O ₃ / SiO ₂ ≦ 0.
31, Al ₂ O ₃ 5 to 9%, provided that SiO ₂ + B ₂ O ₃ +
Al ₂ O ₃ ≧ 83% Li ₂ O _{2 to} 6.5%, Na ₂ O 4 to 7%, K ₂ O
2 to 6.5%, _{however, Li 2 O + Na 2 O} + K 2 O 11~16%, T
iO less than ₂ from 0.05 to 1%, and containing the respective components of Sb ₂ O ₃ 0 to 2% range, the refractive index (nd) of 1.47 to 1.
53, characterized in that the Abbe number (νd) has an optical constant in the range of 60 to 68.

The optical glass of the present invention according to claim 3 is characterized in that the weight loss of the glass calculated by a method for measuring the acid resistance of the optical glass by a powder method is less than 0.35% by weight. I do. Here, the measurement method of the acid resistance of the optical glass according to the powder method, Japanese Optical Glass Industrial Standard; is a method as defined in JOGIS06- ¹⁹⁷⁵ chemical durability of the measurement method of the optical glass (powder method) .

According to the present invention, the glass composition is SiO ₂
—B ₂ O ₃ —Al ₂ O ₃ —R ₂ O (alkali metal oxide) —
Since it is a TiO ₂ system, the refractive index (nd) is 1.47.
It has an optical constant in the range of 1.5 to 1.53 and an Abbe number (νd) of 60 to 68, a low yield point (At), high chemical durability, particularly excellent acid resistance. An optical glass with excellent devitrification and easy to homogenize.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting each component to the above-mentioned composition range in the optical glass of the present invention are as follows.

The SiO ₂ component is an essential component as an oxide forming a glass phase, but if its amount is less than 60%, the chemical durability of the glass will be deteriorated, and if it exceeds 65%, it will be necessary to form a precise mold. A suitable low yield point cannot be obtained.

The B ₂ O ₃ component is also an important component as a glass-forming oxide, and is also an essential component effective for adjusting the viscosity of the glass to an appropriate level when it is melted. If the viscosity is too high, it is difficult to obtain a homogeneous glass. If it exceeds 19%, the chemical durability deteriorates.

In order to obtain a glass having particularly excellent chemical durability, the weight ratio of the B ₂ O ₃ component to the SiO ₂ component should be 0.31 or less.

The Al ₂ O ₃ component is effective for improving the chemical durability of the glass and preventing the phase separation of the glass. However, if the content is less than 5%, the effect is not sufficient, and if it exceeds 9%, the effect is insufficient. The yield point of the glass increases, the viscosity of the glass at the time of molding increases, and the devitrification resistance also deteriorates.

Further, it has a refractive index and Abbe number within the intended range, has a low yield point and viscosity suitable for precise mold press molding, and has particularly excellent chemical durability and devitrification resistance. In order to obtain, the total amount of the SiO ₂ component, the B ₂ O ₃ component, and the Al ₂ O ₃ component should be 83% or more.

The R ₂ O (alkali metal oxide) components, Li ₂ O component, Na ₂ O component and K ₂ O component, have the effect of lowering the yield point of the glass and reduce the melting property during glass production. is an important component for improving, for obtaining these effects, Li ₂ O component, a total of Na ₂ O component and the K ₂ O component, is preferably contained in the range 11-16%.

Among these components, the Li ₂ O component is an important component having an extremely large effect of lowering the yield point of glass, and its effect is maintained while maintaining the devitrification resistance and chemical durability of glass. To obtain, the content should be in the range of 2 to 6.5%.

Further, in order to obtain low yield point characteristics without impairing chemical durability, the Na ₂ O component should be in the range of 4 to 7%, and the K ₂ O component should be in the range of ₂ to 6.5%. Should be in the range.

The TiO ₂ component is a component necessary to prevent coloring of the glass by solarization, to improve the chemical durability, and to have a desired optical constant. Cannot be obtained, and if it is 1% or more, the light transmittance is undesirably deteriorated.

The Sb ₂ O ₃ component can be arbitrarily added as a fining agent for glass, but in order to obtain this effect, its content is sufficient up to 2%.

Further, the optical glass of the present invention contains components other than those described above as necessary for adjusting the optical constant, improving the melting property, chemical durability and devitrification resistance of the glass. For example, MgO, CaO, SrO, B
Components such as aO, ZrO ₂ and F ₂ may be contained up to a total of 3%.

The optical glass of the present invention having the above composition is as follows:
Raw materials such as oxides, carbonates, nitrates, and hydroxides,
After mixing at a predetermined ratio so as to have the above composition, 1
Melt and defoam at a temperature of 200 to 1400 ° C. for about 2 to 4 hours,
After homogenizing with stirring, it can be easily manufactured by casting in a mold or the like and slowly cooling.

[0025]

EXAMPLES Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

Examples of the optical glass according to the present invention (No.
1 to No. Table 15 shows the composition of 15) along with the refractive index (nd), Abbe number (νd), yield point (At), glass transition point (Tg), and the class indicating the powder method acid resistance “RA (P)”. 2 and Table 3. Further, glass having the same composition as that of the example in JP-A-5-193977, which was cited as a conventional example, is cited as a comparative example (No. 1, No. 2), and Table 3 shows the composition and optical constants. Data are shown.
Here, the value of the class indicating the acid resistance “RA (P)” of the powder method is based on the Japan Optical Glass Industry Association standard; JOGIS06-
^It was determined as follows by a method of measuring the chemical durability of the ¹⁹⁷⁵ optical glass (powder method). Example (No. 1 to N
o. 15) and the glasses of Comparative Examples (No. 1 and No. 2) were each ground to a particle size of 420 to 590 μm, and the obtained glass powder sample was placed in a platinum elution basket in a specific gravity gram. Next, the elution basket containing the glass powder sample was placed in a quartz glass round bottom flask containing 80 ml of a 0.01 N nitric acid aqueous solution, and treated in a boiling water bath for 60 minutes. The glass powder sample was taken out from the round bottom flask, and was graded as follows based on the initial weight of the glass powder sample and the weight loss rate (% by weight) calculated from the weight loss. That is, the weight loss rate (% by weight) is 0.20
%, It is grade 1 and 0.20 to 0.35%
Less than 2nd grade, 0.35 to 0.65% less than 3rd grade, 0.6
If less than 5 to 1.20%, it was quaternary, and if less than 1.20 to 2.20%, it was grade 5. That is, in Tables 1, 2 and 3, RA
The smaller the value of the class indicating (P), the higher the acid resistance and the higher the chemical durability.

Each of the glasses of Examples (No. 1 to No. 15) and Comparative Examples (No. 1 and No. 2) had oxides so that the compositions shown in Tables 1, 2 and 3 were obtained. , Carbonates, nitrates, hydroxides, and the like are charged into a platinum crucible and melted at a temperature of 1200 to 1400 ° C. for 2 to 4 hours depending on the degree of meltability determined by each composition. After foaming, stirring and homogenizing, the mixture was poured into a mold and slowly cooled to produce the product. The resulting glass was clear and homogeneous.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

From the above Tables 1, 2 and 3, the optical glasses of Examples (No. 1 to No. 15) of the present invention have a refractive index (nd) of 1.47 to 1.53 and an Abbe number (νd). ) 60
It can be seen that it has an optical constant in the range of ~ 68 and can be sufficiently used as an optical glass. Also, the yield point (At) is less than 550 ° C.
4, no. 9, No. At 14 mag, the yield point (At) is 5
When the temperature is lower than 00 ° C., it is suitable for mold press molding, and the releasability from a molding die is also good. Examples (No. 1) of the present invention shown in Table 1, Table 2 and Table 3
-No. The optical glass of 15) is RA (P)
Is primary or secondary, has a weight loss of less than 0.35% by weight, has more excellent acid resistance than the glass of Comparative Examples (No. 1, No. 2), and has chemical durability. It turns out that it is excellent.

[0032]

As described above, the optical glass according to the present invention has a specific composition range of SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —
Since it is an R ₂ O (alkali metal oxide) -TiO ₂ glass, it has an optical constant with a refractive index (nd) of 1.47 to 1.53 and an Abbe number (νd) of 60 to 68. And
It has a low yield point (At) and good releasability from a mold, and is very suitable for mold press molding for obtaining optical products, particularly precision mold press molding for manufacturing lenses and the like. In addition, it has excellent chemical durability, especially acid resistance, and also has high devitrification resistance and is easy to homogenize.
Suitable for mass production of high quality glass.

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Claims (3)

[Claims] 1. A _{weight%, SiO 2 60~65%, B} 2 O 3 14~19%, Al 2 O 3 5~9%, Li 2 O 2~6.5%, Na 2 O 4~7 %, K ₂ O _{2 to} 6.5% However, each component in the range of Li ₂ O + Na ₂ O + K ₂ O 11 to 16%, TiO ₂ 0.05 to less than 1%, Sb ₂ O ₃ 0 to 2% Contains, and has a refractive index (nd) of 1.47 to
An optical glass having an optical constant of 1.53 and an Abbe number (νd) in a range of 60 to 68. 2. A _{weight%, SiO 2 60~65%, B} 2 O 3 14~19%, however, a weight _{ratio, B 2 O 3 / SiO 2} ≦ 0.31, Al 2 O 3 5~9 %, Where SiO ₂ + B ₂ O ₃ + Al ₂ O ₃ ≧ 83% Li ₂ O _{2 to} 6.5%, Na ₂ O 4 to 7%, K ₂ O _{2 to} 6.5% However, Li ₂ O + Na _{2 O + K 2 O 11~16%,} TiO 2 less than 0.05 to 1%, and containing the respective components of Sb ₂ O ₃ 0 to 2% range, the refractive index (nd) of 1.47～
An optical glass having an optical constant of 1.53 and an Abbe number (νd) in a range of 60 to 68. 3. The glass weight loss calculated by a method for measuring the acid resistance of an optical glass by a powder method is 0.35% by weight.
The optical glass according to claim 1, wherein: