JP2795333B2 - Optical glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention _is, SiO ₂ -TiO 2 -N
a ₂ O—K ₂ O—Li ₂ O-based composition and a refractive index (N
d) is 1.58 to less than 1.71, and Abbe number (νd)
The present invention relates to a novel optical glass having an optical constant in the range of 27 to 34 , a low-temperature softening property imparted with a low transition temperature characteristic, and an improved devitrification resistance.

[0002]

2. Description of the Related Art PbO-containing silicate glass has been well known as an optical glass having the above-mentioned optical constant. However, it does not contain harmful PbO to deal with the pollution problem in the glass manufacturing process, and instead, it contains TiO ₂
Various studies have been made on glass containing. For example, Japanese Patent Publication No. 34-5128 discloses SiO ₂ —TiO ₂ —R
Although an O-based glass is disclosed, this glass has poor devitrification resistance and a high glass transition temperature, and no consideration is given to improvement in low-temperature softening property. Also, Japanese Patent Laid-Open No. 59-1
No. 8131 discloses an alkali silicate glass containing TiO ₂ —Li ₂ O. However, although the softening property at low temperature is improved, the devitrification resistance is poor. As described above, the devitrification resistance tends to deteriorate as the transition temperature of the glass decreases.
Therefore, there is a strong demand for a glass having low-temperature softening properties imparting desired optical properties and low transition temperature properties and having improved devitrification resistance.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional glass in a comprehensive manner, has a predetermined optical constant, maintains low transition temperature characteristics, and is capable of mass production. An object of the present invention is to provide an optical glass having improved devitrification resistance sufficient to achieve the above.

[0004]

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have conducted intensive tests and studies, and as a result, 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, a desired glass having the above-mentioned optical constants and further improved devitrification resistance while maintaining low transition temperature characteristics. Have been obtained, and the present invention has been accomplished.

[0005] The optical glass of the present invention, which achieves the above object,
The feature is that, as described in the claims,
O_Two 38 <~ 55%, TiO_Two 24 <~ 35%, Na
_TwoO5-30%, K_TwoO 3-20%, except for Na_TwoO +
K_TwoO 15-33%,Na _Two O / (Na _Two O + K _Two O)
0.4-0.9,Li_TwoO 0.5 ~4.5%, SrO
+ BaO 09%, As _Two O _Three 0-2%, Sb _Two O _Three
0-1% and the fluoride of one or more metals as F
0-5% of measurementEach component in the rangeConsisting of B _Two O _Three , P
_Two O _Five , Nb _Two O _Five , CaO, ZnO and PbO
And the refractive index (Nd) is less than 1.58 to less than 1.71.
And an Abbe number (νd) in the range of 27 to 34
DoThere.

The reasons for limiting the composition ranges of the above components are as follows.
It is as follows. That SiO ₂ component is an essential component in forming the glass, the amount is 38% or more
When it is below the range , the devitrification resistance of the glass deteriorates, and when it exceeds 55%, it becomes difficult to melt the glass. Although TiO ₂ component is effective to provide highly dispersible in glass, the amount is 24
% Or less , the refractive index is low and the dispersion is low, and if it exceeds 35%, the stability of the glass deteriorates.

The Na ₂ O component is an extremely important component in the glass of the present invention because it has an effect of improving the melting property and stability of the glass. If the amount is less than 5%, the effect is insufficient. If it exceeds 30%, the devitrification resistance deteriorates. The K ₂ O component is an important component because it has an effect of improving the stability of the glass in addition to the improvement of the melting property of the glass, but if the amount is less than 3%, the effect is insufficient. Poor chemical durability. However, Na ₂ O + K ₂
The total amount of the O components should be in the range of 15-33% to maintain the glass's meltability and devitrification resistance. Further Na ₂
When the _{O / (Na 2 O + K} 2 O) ratio of limiting the range of 0.4 to 0.9, because more devitrification resistance of the glass can be maintained preferably.

The Li ₂ O component can be appropriately contained in the glass as an essential component, and can significantly lower the glass transition temperature. Therefore, the Li ₂ O component is an important component in the glass of the present invention. %, The above effect is not sufficient, and if it exceeds 4.5%, chemical durability and devitrification resistance deteriorate. Since each component of SrO and BaO is effective in improving the melting property and stability of the glass, one or more of these components may be added. However, the total amount of one or two of these components is determined by the target optical constant. Up to 9 % to maintain The glass of the present invention may contain, as necessary, one or more metal fluorides in an amount up to 5% as a total amount of F and up to ₂ % of an As ₂ O ₃ component within a range that does not adversely affect the properties of the present invention.
It can be contained for adjusting the optical constant of the glass and improving the melting property and the like. The Sb ₂ O ₃ component can be added up to 1% as a fining agent.

[0009]

Next, examples of the optical glass of the present invention will be described. Table 1 shows examples of composition of the optical glass of the present invention (N
o. 1 to No. 1; 3 ) and comparative examples (No. A and No. B) of conventional glasses were measured for the refractive index (Nd), Abbe number (νd), glass transition temperature (° C.) and liquidus temperature (° C.) of these glasses. It shows the measurement results. All of the glasses described above are weighed and mixed with ordinary optical glass materials such as carbonates, nitrates and oxides, and are weighed using a platinum crucible or the like at a temperature of about 1200 to 1400 ° C. for about 2 to 5 times.
It can be easily obtained by casting in a mold and slowly cooling after homogenization for a time melting. The liquidus temperature in Table 1 is obtained by crushing the glass obtained by the above method, placing the glass on a platinum plate, holding the glass in a temperature gradient furnace for 30 minutes, and observing the devitrification state with a microscope. .

[0010]

[Table 1]

As can be seen from Table 1, all the glasses of the composition examples of the present invention have the desired optical constants and low glass transition temperatures, and the liquidus temperatures of the glass Nos. . A and No. It is lower than the glass of B, and the devitrification resistance is further improved, and the intended improvement effect is remarkable. The glasses of this example are all rich in melting property, easy to homogenize, and have 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-based glass, the refractive index (Nd)
1.58 to less than 1.71, and Abbe number (νd) 27 to
It has an optical constant of 34 and contains no harmful PbO component,
Moreover, the glass transition temperature is significantly lower than that of conventional glass.
In addition, it has excellent devitrification resistance and good meltability . Follow
It is easy to manufacture and directly
This is useful because it is suitable for a mold press for forming and has excellent mass productivity.

──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Hisao Hatta 1-15-30 Koyama, Sagamihara City, Kanagawa Prefecture Oharanai Co., Ltd. (56) References JP-A-63-265840 (JP, A) JP-A-61 JP-A-83645 (JP, A) JP-A-59-8637 (JP, A) JP-A-51-130414 (JP, A) JP-A-59-18131 (JP, A) (58) Fields investigated (Int. . ^6, DB name) C03C 3/062 C03C 3/076 C03C 4/00 G02B 1/02

Claims (1)

(57) [Claims] 1. The composition according to claim 1, wherein the SiO ₂ content is 38 % to 55% by weight.
TiO ₂ 24 < 35%, Na ₂ O 5-30%, K ₂
O 3-20%, provided that Na ₂ O + K ₂ O 15-33
%, Na ₂ O / (Na ₂ O + K ₂ O) is 0.4 to 0.9,
_{Li 2 O 0.5~ 4.5%, SrO} + BaO 0~ 9
_{%, As 2 O 3 0~2%} , Sb 2 O 3 0~1% and 1
Made from the components of the total amount 0-5% range as F species or more metal _{fluorides, B 2 O 3, P 2} O 5, Nb 2 O 5, Ca
O, ZnO and PbO are not contained and the refractive index (N
d) is 1.58 to less than 1.71, and Abbe number (νd)
Has an optical constant in the range of 27 to 34 .