Acidproof, hydrolysis-resistant optical and ophathalmic glass of low density

Abstract

An improved optical glass having an index of refraction of .gtoreq.1.69, an Abbe number of .gtoreq.38, and a density of .ltoreq.3.25 g/cm.sup.3, represents a further development of another optical glass recently provided by the same inventors. The new glass has improved suitability for continuous-tank manufacture and increased acidproofness and differs from the other glass in its content of 0.5-4.0% by weight of P.sub.2 O.sub.5 ; its sum total of SiO.sub.2 +B.sub.2 O.sub.3 +Al.sub.2 O.sub.3 +P.sub.2 O.sub.5 being 38.5-41.5% by weight; and its sum total of MgO+CaO being 13-17.5% by weight. The full glass composition, e.g. is in % by weight:______________________________________ SiO.sub.2 26.0-32.5 B.sub.2 O.sub.3 6.0-12.0 Al.sub.2 O.sub.3 0-3.0 P.sub.2 O.sub.5 0.5-4.0SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =38.5-41.5 Li.sub.2 O 0-5 Na.sub.2 O 0-6 K.sub.2 O 0-8Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 4.5-12.0 MgO 0-8 CaO 9-16MgO + CaO = 13-17.5 SrO 0-6 BaO 0-5 ZnO 0-7 PbO 0-4SrO + BaO + ZnO + PbO = 0-7MgO + CaO + SrO + BaO + ZnO + PbO = 17-24 La.sub.2 O.sub.3 6-11 ZrO.sub.2 5-8La.sub.2 O.sub.3 + ZrO.sub.2 = 13.5-17.5 TiO.sub.2 5-9 Nb.sub.2 O.sub.5 6-11 WO.sub.3 0-4TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 = 14-18La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 =28-33ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 20-26______________________________________

Description

BACKGROUND OF THE INVENTION

Copending, commonly assigned U.S. application Ser. No. 282,787 of July 13, 1981 and its equivalent Federal Republic of Germany application No. P 30 26 605.8 describe an acidproof, hydrolytically stable, optical and ophthalmic glass of low density wherein the sum total of vitrifying agents SiO.sub.2 +B.sub.2 O.sub.3 +Al.sub.2 O.sub.3 +GeO.sub.2 is 25-39% by weight. It can also comprise P.sub.2 O.sub.5 instead of GeO.sub.2. However, it is desired that this glass be improved for certain applications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide optical and ophthalmic glasses of high acidproofness and hydrolysis resistance having an index of refraction n.sub.d of .gtoreq.1.69, e.g., 1.69-1.71, an Abbe number (v.sub.d)>38, e.g., up to about 43, expansion coefficients .alpha..sub.20.degree.-300.degree. C. of about (80-97).multidot.10.sup.-7 and a density (.rho.).ltoreq.3.25, e.g., of 3.15-3.25 g/cm.sup.3, and which can be continuously melted in a melting tank (crucible) and subsequently can be automatically press-molded.

Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.

These objects have been attained by the finding that the suitability of the glass of the earlier applications of continuous-tank manufacture can be still further improved by entirely omitting GeO.sub.2, incorporating P.sub.2 O.sub.5 as a necessary component, and raising the sum total of vitrifying agents SiO.sub.2 +B.sub.2 O.sub.3 +Al.sub.2 O.sub.3 +P.sub.2 O.sub.5 to 38.5-41.5% by weight. In addition, the glass of this invention has even further increased values of acid resistance.

Moreover, the quantitative ranges of the remaining glass ingredients in the novel glass of this invention have been considerably narrowed, in part, as compared with the quantitative ranges disclosed in the earlier applications.

DETAILED DISCUSSION

For example, borosilicate glasses are provided with 26-32.5% by weight of SiO.sub.2 and 6-12% by weight of B.sub.2 O.sub.3. These, as is known, are highly resistant to hydrolysis and chemical attack.

Typical narrowed-down ranges (wt. %) for the components of the novel glasses of this invention are, e.g.,

______________________________________ SiO.sub.2 26.0-32.5 B.sub.2 O.sub.3 6.0-12.0 Al.sub.2 O.sub.3 0-3.0 P.sub.2 O.sub.5 0.5-4.0SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =38.5-41.5 Li.sub.2 O 0-5 Na.sub.2 O 0-6 K.sub.2 O 0-8Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 4.5-12.0 MgO 0-8 CaO 9-16MgO + CaO = 13-17.5 SrO 0-6 BaO 0-5 ZnO 0-7 PbO 0-4SrO + BaO + ZnO + PbO = 0-7MgO + CaO + SrO + BaO + ZnO + PbO = 17-24 La.sub.2 O.sub.3 6-11 ZrO.sub.2 5-8La.sub.2 O.sub.3 + ZrO.sub.2 = 13.5-17.5 TiO.sub.2 5-9 Nb.sub.2 O.sub.5 6-11 WO.sub.3 0-4TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 = 14-18La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 =28-33ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 20-26______________________________________

A preferred class of glasses has the following composition (wt. %)

______________________________________SiO.sub.2 29-32B.sub.2 O.sub.3 7.5-10P.sub.2 O.sub.5 0.5-2.5Al.sub.2 O.sub.3 0-3SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =38.5-41.5Li.sub.2 O 0.5-4Na.sub.2 O 1.5-3.5K.sub.2 O 2.5-7Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 6-10MgO 1.0-5.0CaO 10.0-13.5MgO + CaO = 13-17SrO 0-5ZnO 0-7BaO 0-5PbO 0-4SrO + ZnO + BaO + PbO = 0-7MgO + CaO + SrO + ZnO + BaO + PbO = 16-22La.sub.2 O.sub.3 6-11ZrO.sub.2 5-8La.sub.2 O.sub.3 + ZrO.sub.2 13.5-17.5TiO.sub.2 5-9Nb.sub.2 O.sub.5 6-11TiO.sub.2 + Nb.sub.2 O.sub.5 = 15-17La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 28-33ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 21-25______________________________________

The most preferred glasses have the following compositions (wt. %):

______________________________________ SiO.sub.2 30.5-31.5 B.sub.2 O.sub.3 8.0-9.0 Li.sub.2 O 1.0-2.0 Na.sub.2 O 2.0-4.0 K.sub.2 O 3.0-5.0 MgO 2.0-4.0 CaO 11.0-13.0 La.sub.2 O.sub.3 8.5-9.5 ZrO.sub.2 6.5-8.0 TiO.sub.2 7.0-9.0 Nb.sub.2 O.sub.5 7.0-9.0 SrO 2.0-4.0 P.sub.2 O.sub.5 1.0-2.0or SiO.sub.2 29.0-30.5 B.sub.2 O.sub.3 8.0-10.0 Li.sub.2 O 2.0-4.0 Na.sub.2 O 2.0-4.0 K.sub.2 O 3.0-5.0 MgO 3.0-5.0 CaO 10.0-12.0 La.sub.2 O.sub.3 7.0-8.5 ZrO.sub.2 7.0-8.0 TiO.sub.2 6.0-8.0 Nb.sub.2 O.sub.5 9.0-11.0 P.sub.2 O.sub.5 1.0-2.0 ZnO 3.0-5.0______________________________________

All details of making and using the glasses of this invention are the same as disclosed in parent applications Ser. No. 282,787 unless specified otherwise herein, or inconsistent with anything disclosed herein; e.g., the glasses of this invention will be advantageous in use because of the superior preparation discussed above. Considerations analogous to those discussed in the earlier application can be routinely and conventionally used to determine precise compositions for glasses having desired properties. For example, a portion of the oxygen content of the glass, e.g., up to 1.0 weight percent can, optionally, be replaced by F-atoms.

EXAMPLES

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. In the following examples, all temperatures are set forth uncorrected in degrees Celsius; unless otherwise indicated, all parts and percentages are be weight.

The following examples illustrate typical compositions of this invention and their advantageous properties.

TABLE______________________________________Example 1 2 3 4______________________________________SiO.sub.2 31.05 31.60 31.50 29.74B.sub.2 O.sub.3 8.83 8.50 8.73 9.27Li.sub.2 O 1.10 -- 1.09 3.00Na.sub.2 O 2.74 2.65 2.71 2.18K.sub.2 O 4.15 4.00 4.10 3.30MgO 2.97 4.00 1.96 4.05CaO 12.39 11.30 12.25 10.43La.sub.2 O.sub.3 8.93 7.65 9.49 7.37ZrO.sub.2 7.56 7.30 7.47 7.74TiO.sub.2 8.04 6.50 7.47 6.33Nb.sub.2 O.sub.5 7.50 9.10 7.74 10.70P.sub.2 O.sub.5 1.10 0.85 0.71 1.80SrO 3.56 3.65 4.78 --ZnO -- 2.90 -- 4.09nd 1.70117 1.69291 1.69821 1.70407vd 39.37 39.69 39.73 39.36.rho. 3.20 3.22 3.23 3.19AR.sup.(1) 2 2 2 2CRYSTALL.5.sup.(2)OEG /1040 /1010 /965 /975Kg max/T 2.1/935 1.3/930 1.7/885 2.6/870______________________________________ NOTES TO TABLE .sup.(1) Determination of resistance to acids according to the method described in Schott Catalogue 311 d (1980) "Optisches Glass" (Optical Glass) .sup.(2) Carrier sheet test described in: Grauer, O. H. and Hamilton, D. H., J. Research NBS 44,495 (1950). 5=5 min tempering OEG=upper divitrification temperature Kg max/T-maximum crystal growth rate in .mu./min/ at corresponding temperature (.degree.C.).

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples. From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

1. An optical and ophthalmic glass having n.sub.d 22 1.69, v.sub.d.gtoreq. 38, a density .gtoreq.3.25 g/cm.sup.3, an expansion coefficient .alpha..sub.20.degree.-300.degree. C. of (80-97).multidot.10.sup.-7, a high acid and hydrolysis resistance and sufficient stability for continuous-tank manufacture,

consisting essentially of, in wt. %,

2. A glass of claim 1, of the composition in % by weight.

______________________________________SiO.sub.2 29-32B.sub.2 O.sub.3 7.5-10P.sub.2 O.sub.5 0.5-2.5Al.sub.2 O.sub.3 0-3SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 =38.5-41.5Li.sub.2 O 0.5-4Na.sub.2 O 1.5-3.5K.sub.2 O 2.5-7Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 6-10MgO 1.0-5.0CaO 10.0-13.5MgO + CaO = 13-17SrO 0-5ZnO 0-7BaO 0-5PbO 0-4SrO + ZnO + BaO + PbO = 0-7MgO + CaO + SrO + ZnO + BaO + PbO = 16-22La.sub.2 O.sub.3 6-11ZrO.sub.2 5-8La.sub.2 O.sub.3 + ZrO.sub.2 13.5-17.5TiO.sub.2 5-9Nb.sub.2 O.sub.5 6-11TiO.sub.2 + Nb.sub.2 O.sub.5 = 15-17La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 28-33ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 21-25______________________________________

3. A glass of claim 1, of the composition in % by weight,

______________________________________ SiO.sub.2 30.5-31.5 B.sub.2 O.sub.3 8.0-9.0 Li.sub.2 O 1.0-2.0 Na.sub.2 O 2.0-4.0 K.sub.2 O 3.0-5.0 MgO 2.0-4.0 CaO 11.0-13.0 La.sub.2 O.sub.3 8.5-9.5 ZrO.sub.2 6.5-8.0 TiO.sub.2 7.0-9.0 Nb.sub.2 O.sub.5 7.0-9.0 SrO 2.0-4.0 P.sub.2 O.sub.5 1.0-2.0______________________________________

4. A glass of claim 1, of the composition in % by weight,

______________________________________ SiO.sub.2 29.0-30.5 B.sub.2 O.sub.3 8.0-10.0 Li.sub.2 O 2.0-4.0 Na.sub.2 O 2.0-4.0 K.sub.2 O 3.0-5.0 MgO 3.0-5.0 CaO 10.0-12.0 La.sub.2 O.sub.3 7.0-8.5 ZrO.sub.2 7.0-8.0 TiO.sub.2 6.0-8.0 Nb.sub.2 O.sub.5 9.0-11.0 P.sub.2 O.sub.5 1.0-2.0 ZnO 3.0-5.0______________________________________

5. A lens made of the glass of claim 1 or 2.

6. A lens of claim 5 wherein the lens is an eyeglass lens.