JPH06115969A - Optical glass - Google Patents

Abstract

PURPOSE:To improve the devitrification resistance by including respective components of SiO2, TiO2, Na2O, K2O, Na2O+K2O, Li2O and SrO+BaO at specific weight ratios. CONSTITUTION:Glass raw materials are mixed at a prescribed ratio, thermally melted at 1200-1400 deg.C for 2-5hr, homogenized, then cast into a metallic mold and annealed to provide an SiO2-TiO2-Na2O-K2O-Li2O-based optical glass containing respective components in amounts within the ranges of 25-55wt.% SiO2, 15-35wt.% TiO2, 5-30wt.% Na2O, 3-20wt.% K2O, with the proviso that the total amount of the Na2O and K2O is 15-33wt.%, 0.5-4.5wt.% Li2O and 0-10wt.% total amount of SrO and BaO and, as necessary, <=2wt.% each of As2O3, ZnO and <=2wt.% of total amount of CaO and MgO. This glass is capable of manifesting optical constants of a refractive index (Nd) within the range of 1.58-1.75 and an Abbe's number (rd) within the range of 27-45 and excellent in devitrification resistance and has a low glass transition temperature.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to SiO ₂ --TiO ₂ --N.
a ₂ O-K ₂ O-Li ₂ O-based composition and a refractive index (N
d) has an optical constant in the range of approximately 1.58 to 1.75 and Abbe number (νd) in the range of approximately 27 to 45, and has low-temperature softening property imparted with low transition temperature characteristics and has devitrification resistance. The present invention relates to an improved new optical glass.

[0002]

2. Description of the Related Art PbO-containing silicate glass has been well known as an optical glass having the above optical constant. However, it does not contain harmful PbO in order to deal with pollution problems in the glass manufacturing process, and instead of this, TiO ₂
Various glasses containing Al have been investigated. For example, Japanese Examined Patent Publication No. 34-5128 discloses SiO ₂ —TiO ₂ —R.
Although an O-based glass is disclosed, this glass has a poor devitrification resistance and a high glass transition temperature, and no consideration is given to the improvement of the low temperature softening property. In addition, JP-A-59-1
Japanese Patent No. 8131 discloses a TiO ₂ —Li ₂ O-containing alkali silicate glass, which has improved low-temperature softening property but poor devitrification resistance. Thus, the devitrification resistance tends to deteriorate as the glass transition temperature decreases.
Therefore, there is a strong demand for a glass that has low-temperature softening properties that impart desired optical properties and low transition temperature properties and that has improved devitrification resistance.

[0003]

DISCLOSURE OF THE INVENTION The present invention comprehensively eliminates the above-mentioned drawbacks of conventional glass, has the above-mentioned predetermined optical constant, and maintains a low transition temperature characteristic while being mass-produced. It is to provide an optical glass having improved devitrification resistance that is sufficient.

[0004]

As a result of intensive studies conducted by the present inventors in order to achieve the above-mentioned objects, the inventors have found that SiO ₂ -having a specific composition range not specifically disclosed in the prior art.
In a TiO ₂ —Na ₂ O—K ₂ O—Li ₂ O based glass, the desired glass having the above optical constant and maintaining a low transition temperature characteristic while being further improved in devitrification resistance. It was found that the following was obtained, and the present invention was accomplished.

The characteristics of the optical glass of the present invention that achieves the above-mentioned object are as follows:
_{O 2 35~55%, TiO 2 15~35} %, Na 2 O
_{5~30%, K 2 O 3~20%} , provided that Na ₂ O + K
_{2 O 15~33%, Li 2 O0.5~4.5} % and S
rO + BaO 0 to 10% of each component is contained.

The reason for limiting the composition range of each of the above components is as follows.
It is as follows. That is, the SiO ₂ component is an essential component for forming glass, but if the amount is less than 35%, the devitrification resistance of the glass deteriorates, and if it exceeds 55%, it is difficult to melt the glass. Become. The TiO ₂ component is effective in imparting high dispersibility to the glass, but its amount is 15
When it is less than%, the refractive index is low and the dispersion is low, and when it exceeds 35%, the stability of the glass is deteriorated.

The Na ₂ O component is an extremely important component in the glass of the present invention because it has the effect of improving the melting property and stability of the glass, but if its amount is less than 5%, its effect is insufficient. If it exceeds 30%, the devitrification resistance deteriorates. The K ₂ O component is an important component because it not only improves the meltability of the glass but also has the effect of improving the stability. Chemical durability deteriorates. However, Na ₂ O + K ₂
The total amount of O components should be in the range of 15 to 33% in order to maintain the meltability and devitrification resistance of the glass. Further Na ₂
It is preferable to limit the ratio of O / Na ₂ O + K ₂ O to the range of 0.4 to 0.9 because the devitrification resistance of the glass can be further maintained.

The Li ₂ O component can be appropriately contained in the glass as an essential component and the glass transition temperature can be remarkably lowered, so that it is an important component in the glass of the present invention, but the amount thereof is 0.5. If it is less than 4.5%, the above effect is not sufficient, and if it exceeds 4.5%, the chemical durability and devitrification resistance deteriorate. Since each of SrO and BaO components is effective in improving the melting property and stability of glass, one or more of them can be added, but the total amount of one or two of these components is the target optical constant. To maintain 10%. If necessary, the glass of the present invention may contain one or more metal fluorides in a total amount of F of about 5%, As ₂ O ₃ and Z, as long as the characteristics of the present invention are not adversely affected.
Each component of nO up to about 2%, CaO and M
The total amount of the gO components can be contained up to about 2% for adjusting the optical constant of the glass and improving the meltability. Further, the Sb ₂ O ₃ component can be added up to about 1% as a fining agent.

[0009]

EXAMPLES Next, examples of the optical glass of the present invention will be described. Table 1 shows an example of the composition of the optical glass of the present invention (N
o. 1-No. 10) and the comparative composition examples (No. A and No. B) of the conventional glass of the refractive index (Nd), Abbe number (νd), glass transition temperature (° C) and liquidus temperature (° C) of these glasses. It shows the measurement results. In the case of the indicated glasses, ordinary optical glass raw materials such as carbonates, nitrates and oxides are weighed and mixed, and this is used in a platinum crucible or the like at a temperature of about 1200 to 1400 ° C. for about 2 to 5
It can be easily obtained by homogenizing the melt for a period of time, casting it in a mold, and slowly cooling it. The liquidus temperature in Table 1 is obtained by crushing the glass obtained by the above method, placing it on a platinum plate, holding it in a temperature gradient furnace for 30 minutes, and observing the devitrification state with a microscope. .

[0010]

[Table 1]

[Table 1]

[Table 1]

[Table 1]

As shown in Table 1, all the glasses of the composition examples of the present invention have the desired optical constants and a low glass transition temperature, and the liquid phase temperature is glass No. of the comparative example which is conventionally known. ． A and No. It is lower than the glass of B and has further improved devitrification resistance, and the intended improvement effect is remarkable. Each of the glasses of this example has a high meltability, is easily homogenized, and has good chemical durability.

[0012]

As described above, the optical glass of the present invention has a novel characteristic composition range of SiO ₂ —TiO ₂ —Na ₂ O—.
Since it is a K ₂ O—Li ₂ O type glass, it has a refractive index (Nd) of about 1.58 to 1.75 and an Abbe number (νd) of about 27 to 4
It has an optical constant of 5 and a low glass transition temperature and is harmful to P.
It is useful because it does not contain a bO component, and has excellent devitrification resistance, good meltability, and excellent mass productivity as compared with conventional glass.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisao Hatta 1-15-30 Koyama, Sagamihara City, Kanagawa Prefecture Ohara, Inc.

Claims (1)

[Claims] 1. By weight%, SiO ₂ 35-55%, T
iO ₂ 15-35%, Na ₂ O 5-30%, K ₂ O
3 to 20%, but Na ₂ O + K ₂ O 15 to 33%, L
i ₂ O 0.5-4.5% and SrO + BaO 0-
An optical glass containing each component in the range of 10%.