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Home , Beryllium oxide, Boron trioxide, Lanthanum oxide, Strontium oxide

Patented May 11, 1954 2,678,281

UNITED STATES PATENT OFFICE 2,678,281 OPTICAL, Walter Geffcken and Gerd Rehs, Landshut (Bay.), Germany, assignors to Jenaer Glas werk Schott & Gen., Mainz, Rheinland-Pfalz, Germany No Drawing. Application May 6, 1953, Serial No. 353,436 Claims priority, application Germany May 26, 1952 5 Claims. (C. 106-53) 1. 2 Optical so far known, with a refractive the invention, they should preferably be melted in index ind greater than 1.70 and a value of the the platinum crucible. Abbe number 2) of between 42 and 52 either con Naturally, additional glass components such as tain considerable amounts of the expensive tan alkali and alkali , (MgO), talum, poisonous , or radioactive thori oxide (TaO5) and others can be intro um, Or show an inclination to crystallize, as do duced in quantities of at the most 3% all told, glasses With a high content of oxide Without thereby affecting the nature of the in (CdC), or else are strongly colored, as for in vention. stance glasses with a high percentage of The table below shows a number of examples oxide (WO3). By the present invention it be () of the glasses of the invention in respect to com comes possible to produce, without employing position and optical character. any of the substances named, colorless and not too expensive glasses of the desired optical char acteristics and which are free from any tendency SiO---- 5.9 2.0 ------4.0 ------4.0 4.0 4.0 to crystallize. This is accomplished by using a 5 B2O3--- 37.6 36.0 37.6 37.3 42.0 41.3 32.7 32.7 32.7 La2O3- 33.7 25.0 26.7 25.7 26.4 32.4 38.0 26.8 29.0 composition of 25% to 38% of oxide ZrO2---- 7.9 3.0 2.5 7.4 7.8 8.1 7.5 7.5 7.5 (Ta2O3), 4% to 18% oxide (PbO), 30% to PbO---- 4.0 4.0 11.3 10.7 12.1 6.1 6.8 18.0 15.8 CaO---- 10.9 5.0 14.5 10.9 11.7 12.1 1.0 11.0 11.0 48% trioxide (B2O3), and at the most 6% SrO------8.0 ------silicium dioxide (SiO2), while the content of cal BaO----4------5.0 ------ZnO------17.0 7.4 4.0 ------cium oxide (CaO), oxide (SrO), ld------i.7051.70 i. 7171.717.77 1.720.738 1744 1,744 oxide (BaO), and oxide (ZnO) combined is ------52.0 50.0 47.8 47.9 48.0 50,3: 48.5 43.7 44.7 at least 9% but does not exceed 30%. Into these glasses, oxide (ZrO2) can We claim: be introduced without difficulty in proportions of 1. Optical glass of a ind greater up to 8.5%, at a considerable increase in chemi 25 cal stability. than 1.70 and a 2-value between 42 and 52 being Generally Speaking, it is best to hold the con free from tantalum oxide, oxide and tent of the bivalent components named, CaO, and containing from 25% to 38% SrO, BaO, ZnO together under 22%, because the La2O3, 4% to 18% PbO, 30% to 48% B2O3, at the melts Will then be particularly free from tending most 6% SiO2, and 9% to 30% of CaO plus SrC) to Crystallize. plus BaO plus ZnO, It is to be recommended not to let the baryta. 2. Optical glass according to claim 1 containing content rise above 5%, as otherwise a tendency up to 8.5 of ZrO2. toWard Crystallization is to be feared. 3. Optical glass according to claim 1, contain If refractive-index figures of about 1.715 and ing CaO plus SrO plus. BaO plus ZnO to an above are desired, the combined content of La2O3 amount of less than 22%. and PbO should be held at over 37%. 4. Optical glass according to claim 1 containing The Substitution of for an BaO to an amount of not Over 5%. equal share of lead oxide but with the glass com 5. Optical glass according to claim 1 contain position otherwise unaltered does not affect the 40 ing a2O3 plus PbO to an amount of over 37%. 22d-Value, but reduces the 2-value by about 0.4 per 1 per cent of Oxide replaced, No references cited, Because of the high fluidity of the glasses of