Patented June 7, 1949 2472448

UNITED STATES PATENT OFFICE 2472,448 THAILL}{{UMI-SILECA || B. GLASS Kuam-BHan Sum, Rochester, N.Y., assigmor to East mam Kodak Company, R0chester, N. Y., a cor poration of New Jersey Application August 9, 1946, Serial No. 689,528 4. Claims. (CI, 106-52) 1 • 2 This invention relates to glasses having unusual properties, chemical durability, melting opera Optical properties and specifically to silicate glaSS tions and glaSS formation. C0ntaining thallium in considerable amount. In the following table are giVen Several Spe In general flint glaSSes have higher dispersions cific examples, W. indicating weight percent, and or lower Abbe values, as compared to other types 5 M mole percent. The table also gives the Values Of Optical glaSSes of the same refractive indices; of the refractive index for the D line (np) and Or lower refractive indices for the same disper the Abbe Values (v), where known; and also in Sions Or Abbe values. It is often desirable, for the column headed “Temp,” the apprOximate 0ptical purposes, to have glaSSes with even higher melting temperature in degreeS centigrade, T"able III

SiO2 NaO0,5

31.0 16, 1 16), 5 19,8 26. 2 1902 32. 5 1, 9334 31,8 25.4 dispersions or lower Abbe Values than those at As instanced in Examples 4 to 7, Sodium oxide or present, available. I have discovered that glaSSeS its equivalent, potassium oxide may be intro haVing these desirable properties may be obtained duced. Other Oxides, particularly those Of bOrOn by the use of thallium Oxide component in large (up to 15 weight per cent or 40 mole per Cent) or an10untS. aluminum (up to 10 weight per cent or 15 mole ? have found particularly UISeful SU1Ch glaSS haV per Cent) OT ColumbiUlm, and tantalum, may alSO ^ ing present a, Substantial amount Of titanium be included, the last two ment?Oned being Sub Oxide. A. glaSS COmpOSed Simply Of the OxideS Of 30 stituted for titanium in whole or in part. Such titanium, Silicon, and thallium may be made and additions may improve the qualities of the glaSS Figure 1. ShoWS the approximate limits of glaSS Such as chemical and physical durability, and fO!"rì8,tion Of Stach a, System in both mole and a.VOidance of deVitrification. When additional weight percentages, these being indicated by lines OxideS are included, the amount Of Oxides men A and B. respectively. Since Na2O; Tl2O; etc. are tioned in Table I, is less than the range therein empirical formulaS, it is equally eXpedient and Specified. rnore conVenient to adopt the form NaO0.5; Figure 2 is a Chart the Coordinates of which TIO0.5, et.C. are mp and v, showing at line A the approximate The Sar?me information is given in tabulatiOn limit Of the ValueS Of COmmercially a Vailable form in the following table, Showing the appTOXi 40 , glaSSeS. The points designated 2, 3, 5 and 6, Imaüe limit, b0th in Weight and mole percentageS Show the Values giVen in Table II for the eX amples similarly numbered. This shows graphi Table I cally the unusual Optical properties of these glaSSeS. \ weight, I Mole, 4õ Since thallium compounds, particularly in Va per cent | per Cent por form, attack platimum rapidly, these glaSSes are melted in VeSSelS Of high Silica glaSS. As is

T&};1\}2- - 6{} | 3; usual in glaSS-making the ingredient:S may be in SiO2--- 4-28 Î0-54 troduced in C0mpounds other than the Oxides, 50 being transformed in the furnace. Thallous mi The addition of other Oxides Of COurse changeS trate has been found Satisfact0ry in making up the liimits for the three given above. the batch. Since thallous compounds are VOla Glasses may form outside these limits, but I tile at relatively low temperatures, it is important have found that those within them are particu to “bake” the batches at about 300° C. for about larly Valuable from the Standpoint of optical One hour to insure the initial reactions betweem

2,472,448 3 4 the ingredients, So that thallous comp0unds Will weight of thallous oxide, 64 to 91 per cent; ti not be present in free forms, thereby leSSening tanium dioxide, 5 to 20 per Cent; Silica, 4 t0 28 or eliminating the Volatilization lOSS. These per Cent. glasses melt at temperatures between 900° and 3. An Optical glaSS composition comprising eS 1400° C., the approximate temperatures for the 5 Sentially by weight: thallous oxide, 40 to 91 per particular examples given being Shown in Table cent; silica, 4 to 30 per Cent; 0xide Selected from II. Usually batches containing large amountS Of the group COnsisting Of the Oxides Of SOdium and Silica or alumina require high temperature for pOta.SSium and mixtures theTeOf, 0 to 10 per Cent; melting (1400° C.) and those containing fela aluminum oxide, 0 to 10 per cent; b0rOn Oxide, tively large amounts of thallium lower the melti 10 0 to 15 per cent, Oxide Selected from the group ing temperatureS. conSiSting of the Oxides of titanium, Columbium, In the systems of Table I, an average tempera= and tantalum, and mixtures there0f, 5 t0 20 per ture of about 1050° C. is sufficient for melting. Cent. In each System, in practice, a minimum tempera 4. An optical glaSS C0mposition C0mprising eS ture of melting Should be eXperimentally deter 15 Sentially by Weight: thallOuS Oxide, 40 to 55 per mined for individual formulas and used When cent; titanium dioxide, 20 t0 28 per cent; silica, eVer pOSSible to leSSen the VOlatilization l0SS Of 14 tO 30 per Cent; Oxide SeleCted frOIn the group thallium and Solution of the material of the high COrìSiSting of the OXides Of SOdium and pOta,SSium, silica, container. The molding temperatureS Of and mixtureS thereOf, 5 tO 10 per Cent, the glasses are between 300-650° C. depending on 20 the composition. KUAN-HAN SUN. Most of the glaSSes, particularly those With low alkali content, are durable against moisture REFERENCES CITEL) attack. The glaSSeS haVing a high thallium C0n The follOWing references are Of record in the tent have a distinct yellow t?nt. 25 file Of this patent: HaV?ng thus dscribed my invention, what I claim is: UNITED STATES PATENTS 1. An Optical glass consisting of the heaf-reac NLimber Name Date tion product of a batch COmSiSting Of Compatible 1,607,817 Dennis ------NoV, 23, 1926 oxides, at least ninety per cent by Weight Of 30 which COnsists of Silica, thaÎloUS Oxide, and ti OTHER, REFERENCES tanium dioxide, Ser. No. 395,364, Berger et al. (A. P. C.), pub 2. An Optical glaSS Comp0Sition COnSiSting by lished May 11, 1943.