Strengthenable, high neodymium-containing glasses

Abstract

A strengthened high NdO.sub.3 -containing glass has the composition of, in weight percent______________________________________SiO.sub.2 40-60Nd.sub.2 O.sub.3 10-30As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-1B.sub.2 O.sub.3 5.15Na.sub.2 O 3-18ZnO 0.1-10Li.sub.2 O 0-3K.sub.2 O 0-3Al.sub.2 O.sub.3 0-7PbO 0-15MgO 0-3CaO 0-3BaO 0-3SrO 0-3.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5Pr.sub.6 O.sub.11 0-1.______________________________________

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No. 07/463,225 (Atty. Dkt. SGT 15), now U.S. Pat. No. 5,039,631 issued Aug. 13, 1991 which is entirely incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates to strengthenable glasses having a high neodymium content.

Various glasses are known having relatively high neodymium oxide contents. For example, the following United States patents disclose glasses having amounts of neodymium which can exceed about 10 wt.%: U.S. Pat. Nos. 4,521,524 (contrast enhancement filters); 4,288,250 (contrast enhancement filters); 4,769,347 (contrast enhancement filters); and 3,947,281 (high modulus glasses). Also known are glasses having contents up to about 10 wt.% of neodymium such as U.S. Pat. Nos. 4,376,829 (cathode ray tube glass) and 4,390,637 (cathode ray tube glass). However, no discussion of strengthenability of these glasses is given.

Of course, strengthening of glasses per se has long been known for various glasses such as crown glasses. See, e.g., J. S. Stroud, Glass Technology, Vol. 29, No. 3, June 1988, 108-114, and U.S. Pat. Nos. 4,036,623; 4,022,628; and 4,012,131, wherein ZnO is used to enhance chemstrengthening in conventional ophthalmic glasses. Chemstrengthenability of a glass containing 15-35 wt.% of La.sub.2 O.sub.3 is also known (U.S. Pat. No. 3,997,249).

However, a need exists for further improvements and particularly for development of a high neodymium oxide-containing glass which is satisfactorily strengthenable, chemically or physically.

SUMMARY OF THE INVENTION

This invention relates to high Nd.sub.2 O.sub.3 -containing glasses, e.g., particularly for ophthalmic uses, which have an excellent capability for chemical strengthening and physical strengthening.

Thus, in one aspect, this invention relates to a glass composition having the following components:

TABLE 1______________________________________Compositions in Weight Percent* General Preferred Most Preferred______________________________________SiO.sub.2 40-60 45-60 50-55Nd.sub.2 O.sub.3 10-30 20-30 22-26As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-1 0-0.5 0.2-0.4B.sub.2 O.sub.3 5-15 5-10 6-8Na.sub.2 O 3-18 10-15 11-13ZnO 0.1-10 1-7 2-5Li.sub.2 O 0-3 0 0K.sub.2 O 0-3 0 0Al.sub.2 O.sub.3 0-7 0 0PbO 0-15 0 0MgO 0-3 0 0CaO 0-3 0 0BaO 0-3 0 0SrO 0-3 0 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7 0 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5 0 0Pr.sub.6 O.sub.11 0-1 0 0______________________________________ *0 (zero) amounts refer to essentially 0, i.e., no positive additions of these components. Occasionally, trace amounts may be unavoidably included due to batch component impurities. TABLE 2______________________________________Calculated Compositions in Mole Percent*Oxide/Mole % General Preferred Most Preferred______________________________________SiO.sub.2 54-75 60-70 65-70Nd.sub.2 O.sub.3 3-6 5-6 5.4-5.6As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-0.4 0-0.2 0-0.2B.sub.2 O.sub.3 5-17 5-10 6-9Na.sub.2 O 3-18 10-18 15-17ZnO 0.1-10 1-7 2-4Li.sub.2 O 0-3 0 0K.sub.2 O 0-3 0 0Al.sub.2 O.sub.3 0-7 0 0PbO 0-4 0 0MgO 0-3 0 0CaO 0-3 0 0BaO 0-3 0 0SrO 0-3 0 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7 0 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5 0 0Pr.sub.6 O.sub.11 0-0.5 0 0______________________________________ *0 (zero) amounts refer to essentially 0, i.e., no positive additions of these components. Occasionally, trace amounts may be unavoidably included due to batch component impurities.

These glasses are useful for all applications wherein a high-Nd.sub.2 O.sub.3 content glass is useful, e.g., as a contrast enhancement glass, e.g., for sunglasses, having particular applicability for users where high contrast is an advantage, e.g., for shooters or hunters, as filters, especially CRT filters, e.g., in accordance with conventional procedures, e.g., per the references cited above, etc. "Contrast enhancement" refers primarily to absorption by the glass of more background radiation than object radiation.

In another aspect, this invention relates to a glass having the composition given above, except also containing an amount of CeO.sub.2 in the range of 0.1-2 wt.% (0.05-1.0 mole %), preferably in the range of 0.1-1 wt.% (0.05-0.5 mole %), and most preferably in the range of 0.4-0.6 wt.% (0.2-0.3 mole %). When cerium is present, the maximum amount of As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 should be 0.3 wt.% to avoid unacceptable solarization. The cerium oxide also acts as a refining agent. Ce-containing glasses, for example, are useful as UV-attenuated glasses. For example, they achieve 99 percent UV attenuation at a wavelength of 350 nm.

As also discussed below, the glasses can optionally contain coloring-effective amounts of conventional colorants, whereby the glasses can be employed as color enhancement filters also, i.e., as filter glasses for the visible region.

The strengthenability of the glasses of this invention is achieved very advantageously, despite the high Nd.sub.2 O.sub.3 contents by the compositional features, for example, regarding inclusion of ZnO and Na.sub.2 O, and exclusion of K.sub.2 O, inter alia.

If the amount of sodium oxide is less than 3 wt.%, then unsatisfactory strengthening, especially chemical strengthening, will be obtained. If the amount of sodium oxide is greater than 18 wt.%, devitrification increases. Also, the resultant melt can unacceptably attack the refractory material of the melt tank. Other end point amounts for the sodium oxide weight percent range are 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 18.

It has been found, surprisingly, that, even in this high Nd content system, zinc oxide is effective in assisting the ion exchange process as is known for conventional ophthalmic glasses. (See, e.g., U.S. Pat. No. 4,012,131.) When less than 0.1 wt.% is included, the resultant chemstrengthenability is less preferred. In addition, devitrification increases and chemical durability is lowered. Preferably, the amount of ZnO is at least 0.2 wt.%. When amounts of ZnO greater than 10 wt.% are included, unsatisfactory phase separation occurs. Other end point limits for ZnO include 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 wt.%.

It is also important that the amount of K.sub.2 O be 0-3 wt.%. If an amount greater than 3 wt.% is included, the chemstrengthening process is adversely affected. For example, the modulus of rupture (MOR (nm/cm)) becomes worse. Alternative end point wt.% limits for K.sub.2 O include 0.5, 1, 1.5, 2, 2.5, and 3.

Similarly, if the amounts of CaO, BaO, or SrO exceed 3 wt.%, there will be an adverse influence on the chemstrengthenability of the glass by interference effects during the chemstrengthening process. For example, depth of layer (DOL (.mu.m)) and/or MOR worsen. It has been noted, however, that at higher CaO contents in this range, the adverse effects on the ion exchange process can be offset by the addition of relatively larger amounts of ZnO and/or MgO within the ranges given herein. Alternative weight percent end points for each of these components include 0.5, 1, 1.5, 2, 2.5, and 3.

Amounts of MgO greater than 3 wt.% cause an unfavorable increase in the melting temperature. Alternative weight percent end point limits for MgO include 0.5, 1, 1.5, 2, 2.5, and 3.

Inclusion in the glasses of this invention of amounts of PbO greater than 15 wt.% also will cause effects unacceptably interfering with the chemstrengthening process, e.g., worsening DOL and/or MOR. Alternative end point weight percent limits for this ingredient include 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 wt.%. In glasses including CeO.sub.2, Ti-Ce and Pb-Ce can form a color center which will shift some of the color effects. Where these effects are unacceptable, of course, less Ti and less Pb, respectively, should be employed within the range of this invention.

Amounts of Li.sub.2 O greater than 3 wt.% cause undesirable crystallization of the glass, i.e., devitrification instability. Alternative end point weight percent limits for this component include 0.5, 1, 1.5, 2 and 2.5 wt.%.

Amounts of Al.sub.2 O.sub.3 greater than 7 wt.% cause unacceptable melting difficulties. Alternative end point weight percent limits for this glass component include 1, 2, 3, 4, 5, 6, and 7.

For glasses not containing CeO.sub.2, the total amount of the refining agents As.sub.2 O.sub.3 and/or Sb.sub.2 O.sub.3 should be at most 1 wt.%. An especially preferred amount is about 0.3 wt.%. When CeO.sub.2 is present, the permissible amounts of As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 are significantly lowered due to an incompatibility causing solarization. Thus, with CeO.sub.2 present, the amount of As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 is 0-0.3 wt.%, preferably 0 wt.%.

When amounts of network former SiO.sub.2 less than about 40 wt.% are included, unacceptable devitrification occurs. When amounts greater than 60 wt.% are included, maximum Nd content and/or chemstrengthenability are adversely affected. Alternative end point weight percent limits for this ingredient include 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, and 60 wt.%.

When amounts of Nd.sub.2 O.sub.3 less than 10 wt.% are included, unsatisfactory contrast enhancement is achieved. When amounts greater than 30 wt.% are included, devitrification is unacceptable. Alternative end point weight percent limits for this ingredient include 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30.

When amounts of the fluxing agent B.sub.2 O.sub.3 less than about 5 wt.% are included, meltability is unacceptable. When amounts greater than about 15 wt.% are included, phase separation occurs and devitrification is unacceptable. Alternative end point weight percent limits for this ingredient include 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15.

The minimum amount for effective UV attenuation of CeO.sub.2 is typically about 0.1 wt.%, most preferably at least 0.5 wt.%. When amounts of this UV-attenuator greater than 2 wt.% are included, the maximum permissible amount of Nd is lowered. Alternative end point weight percent limits include 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0. An especially preferred amount is about 0.5 wt.%. When Pb and/or Ti is also present in the glass, UV-attenuation can also be achieved by Ce/Pb and/or Ce/Ti combinations.

When amounts of TiO.sub.2 or Pr.sub.6 O.sub.11 greater than 5 wt.% and 1 wt.%, respectively, are included, color mismatches may occur. This is an important effect for the applications of the glass of this invention where color is important, e.g., in contrast enhancement applications for cosmetic reasons and in color filter applications for obvious reasons.

For many applications of the glasses of this invention, additional colorants will not be desired, e.g., where the inherent coloration (purplish) caused by the neodymium oxide content is satisfactory per se. Amounts of conventional colorants can still be included, as long as the amounts of each are less than those wherein each ingredient is effective as a major colorant. Typically, such amounts will be as follows for several conventional colorants:

TABLE 3______________________________________ Wt. %*______________________________________ Cr.sub.2 O.sub.3 <0.005 CuO <0.02 MnO <0.02 CoO <0.0005 Fe.sub.2 O.sub.3 <0.035 NiO <0.02 TiO.sub.2 <5.0 V.sub.2 O.sub.5 <0.02 Er.sub.2 O.sub.3 <0.1______________________________________ *Amounts generally too low for effective coloring effects, e.g., amount permitted as impurities.

Of course, where the coloring effect of such conventional additives is desired, an effective amount greater than those stated above can routinely be employed. Typically, the upper limit on the amount of each colorant will be routinely chosen, e.g., for cosmetic and performance reasons with respect to the final color produced, as long as there is no adverse effect on the important properties of the glass of this invention. Typically, the total amount of all colorant additives will be less than 7 wt.%, preferably less than 5 wt%, unless indicated otherwise herein. Normally, that component will be exchanged for neodymium on an ion for ion basis. Suitable colorants include those listed in Table 3. Their use to custom contour the spectral response of the glass is analogous to U.S. Pat. No. 4,769,347 and 4,521,524.

Contents of Pr.sub.6 O.sub.11 in the glasses of this invention will typically occur due to unavoidable impurities in the Nd.sub.2 O.sub.3 which is commercially available. For example, for 95 percent pure Nd.sub.2 O.sub.3, the resultant impurity content in the glasses of this invention will typically be in the range of about 1.9-3.7 wt.%. This is equivalent to an addition to the glass containing absolutely pure Nd.sub.2 O.sub.3 of about 0.9 wt.% Pr.sub.6 O.sub.11.

When the glasses of this invention are employed as contrast enhancement eyeglass lenses, they are preferably shaped conventionally into a suitable form for use and conventionally combined with typical eyeglass frames. When employed as color enhancement filters, similar processing can be employed. Similarly, conventional processing can be used to work up the glasses for use as CRT filters. The latter will typically be designed for the typical CRT phosphor emission lines, P-22 and P-43. See, e.g., U.S. Pat. No. 4,769,347.

In view of the unique combination of ingredients given above, the glasses of this invention can be very well chemstrengthened using conventional techniques such as those mentioned in the Stroud and other references, above. Typically, a crown-bath solution can be used, e.g., 99.5 percent KNO.sub.3 and 0.5 percent silicic acid, at a temperature in the range of about 480.degree.-550.degree. C. for an exchange time of, e.g., 16 hours or in the range of 8-24 hours. Typically, a preferred exchange temperature will be approximately 30.degree. lower than the strain temperature of the glass. Determination of optimum chemstrengthening layer thicknesses can be effected routinely. Typically, acceptable thicknesses of a chemstrengthened layer will be above 30 .mu.m, preferably about 50 .mu.m; however, narrower and larger thicknesses are fully included. Typical surface compression values achievable are about 1600-2200 nm/cm.

Strengthening by physical tempering can also be very advantageously performed in conjunction with the glasses of this invention. A suitable procedure involves hot air blowing at about 700.degree. C. to T.sub.g .degree. C.+100.degree., followed by room temperature air blowing for quenching. Typically, the hot air treatment lasts for about 2-3 minutes.

The glasses of this invention can be prepared routinely by using normal batch components corresponding to the above-mentioned oxides, followed by conventional melting in an appropriate crucible, e.g., a platinum or quartz crucible, e.g., at melt temperatures of, for example, 1300.degree.-1450.degree. C. A general rule of thumb for suitable conditions for air hardening is that temperatures should be about T.sub.g +100.degree. C. and hot air soak should continue for one minute for every mm of sample thickness.

Preferred properties of the glasses of this invention include:

______________________________________ Transmission (%) With UV Without UV.lambda. Attenuation Attenuation______________________________________680 <65 <65570-590 <1 <1530 <10 <10350 <0.5 <4CTE.sub.20-300.degree. C. (.times. 10.sup.-7) <100 <100______________________________________

The CTE properties are particularly useful for physical tempering. As can be seen, the glasses have an absorption peak at 580 nm. They have essentially no absorption peak at 490 nm. These properties contribute toward their usefulness as CRT filters.

Without further elaboration, it is believed that one of ordinary skill in the art can, utilizing 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 foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight.

The entire texts of all applications, patents, and publications, if any, cited above and below are hereby incorporated by reference.

TABLE 4__________________________________________________________________________ Examples 1 2 3 4 5* 6 7* 8* 9 10* 11 12__________________________________________________________________________Oxide wt. %SiO.sub.2 56.80 54.82 51.16 43.01 20.52 40.01 33.01 25.01 51.16 46.00 49.16 53.11Nd.sub.2 O.sub.3 14.70 20.54 27.99 27.99 54.0 27.99 27.99 27.99 27.99 27.99 27.99 24.02As.sub.2 O.sub.3 0.30 0.29 0.27 0.27 0.2 0.27 0.27 0.27 0.27 0.27 0.27 0.28BaO 3.00B.sub.2 O.sub.3 7.60 7.34 6.85 15.00 9.72 15.00 22.00 30.00 7.11Na.sub.2 O 14.62 14.10 13.16 13.16 13.16 13.16 13.16 13.16 13.16 13.16 13.67ZnO 3.00 2.90 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 1.81Al.sub.2 O.sub.3 12.96 3.00 3.00 3.00 6.85 12.01 6.85Li.sub.2 O 2.70 2.00Oxides mol. %SiO.sub.2 67.93 67.93 67.93 57.98 39.69 54.84 45.85 35.28 69.64 64.47 65.13 67.93Nd.sub.2 O.sub.3 3.14 4.54 6.63 6.73 14.85 6.84 6.94 7.04 6.80 7.00 6.62 5.48As.sub.2 O.sub.3 0.11 0.11 0.11 0.11 0.12 0.11 0.11 0.12 0.11 0.11 0.11 0.11BaO 1.40B.sub.2 O.sub.3 7.83 7.84 7.84 17.43 16.21 17.73 26.35 36.49 7.84Na.sub.2 O 16.93 16.93 16.93 17.18 17.47 17.70 17.98 17.35 17.86 16.89 16.93ZnO 2.65 2.65 0.56 0.57 0.58 0.58 0.59 0.58 0.54 0.56 1.71Al.sub.2 O.sub.3 14.85 2.44 2.47 2.51 5.52 9.97 5.37Li.sub.2 O 10.49 5.32Stability Good Good PBA PBA Poor PBA Poor Poor PBA Didn't PBA PBA Even Melt__________________________________________________________________________ Examples 13 14 15 16 17 18 19 20 21 22 23 24__________________________________________________________________________Oxide wt. %SiO.sub.2 53.0 46.48 51.79 52.59 53.66 53.11 53.39 51.79 49.94 51.53 49.69 52.72Nd.sub.2 O.sub.3 24.05 22.32 22.28 23.87 22.14 24.02 23.04 23.03 22.90 22.91 22.79 22.75As.sub.2 O.sub.3 0.28 0.26 0.29 (1.02) (1.04) 0.28 (0.52) (0.52) (0.52) (0.52) (0.51) (0.51) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2)BaOB.sub.2 O.sub.3 6.23 6.58 7.23 7.04 7.18 7.11 7.15 7.14 7.10 7.11 7.07 7.06Na.sub.2 O 13.64 12.64 12.24 11.81 13.15 13.08 13.08 14.70 14.62 13.01 12.94 10.51ZnO 2.80 1.68 5.39 3.67 2.84 1.81 2.82 2.82 4.92 4.93 7.01 2.79Al.sub.2 O.sub.3Li.sub.2 O 0.79 (10.04) (PbO)K.sub.2 O 3.65Oxides mol. %SiO.sub.2 67.93 64.20 65.14 67.93 67.93 67.93 67.93 65.93 63.93 65.93 63.93 67.93Nd.sub.2 O.sub.3 5.50 5.50 5.00 5.50 5.00 5.50 5.23 5.23 5.23 5.23 5.23 5.23As.sub.2 O.sub.3 0.11 0.11 0.11 (0.46) (0.46) 0.11 (0.23) (0.23) (0.23) (0.23) (0.23) (0.23) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2) (CeO.sub.2)BaOB.sub.2 O.sub.3 6.88 7.84 7.84 7.84 7.84 7.84 7.84 7.84 7.84 7.84 7.84 7.84Na.sub.2 O 16.93 16.91 14.91 14.77 16.12 16.93 16.12 18.12 18.12 16.12 16.12 13.12ZnO 2.65 1.71 5.00 3.50 2.65 1.71 2.65 2.65 4.65 4.65 6.65 2.65Al.sub.2 O.sub.3Li.sub.2 O 2.00 (3.73) (PbO)K.sub.2 O 3.00Stability Fair Fair PBA PBA Good Good Good Fair Fair Fair Fair__________________________________________________________________________ Properties 1 2 13 14 15 17 18 19 21 22 23 24__________________________________________________________________________Ion Exchange 530.degree. C.16 hr.DOL (.mu.m) 50 41 40 48 50 52 50 55 <50MOR (nm/cm) 1642 1280 1609 1612 2061 1916 1771 2294 <1770n.sub.d 1.55 1.55947 1.56782 1.56697 1.56659CTE.sub.20-300 .times. 10.sup.-7 /.degree.C. 92 90.0 86.1Tg/.degree.C. 545 582 576Ts/.degree.C. 721 723.delta./gcm.sup.-3 2.86 2.98 2.99 2.99__________________________________________________________________________ 1 2 13 14 15 17 18 19 21 22 23__________________________________________________________________________Transmission (%).lambda. (nm)770 49.0 51.5760 11.3 12.8750 0.6 0.7740 0.5 0.7730 35.1 36.1720 81.4 81.8710 87.5 87.6700 84.4 84.6690 63.8 65.5680 60.3 61.9670 78.4 79.0660 89.1 89.0650 89.7 89.6640 87.1 87.1630 79.1 79.8620 84.1 84.4610 48.0 52.2600 6.1 8.1590 0.2 0.2580 0.2 0.2570 0.8 0.8560 74.4 75.5550 80.4 81.2540 52.3 55.0530 4.3 5.7520 21.0 23.5510 21.5 24.2500 58.7 60.7490 79.6 80.1480 50.0 52.1470 49.8 51.7460 58.3 59.6450 74.8 75.3440 75.6 75.8430 43.1 44.8420 85.5 83.6410 89.6 85.8400 89.5 83.3390 89.2 78.8380 87.9 70.2370 90.0 57.0360 4.0 1.5350 1.0 <0.5340 48.0 <0.5__________________________________________________________________________ *Comparative Poor but acceptable

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. A high Nd, chemically strengthenable glass consisting essentially of, in weight percent

______________________________________SiO.sub.2 40-60Nd.sub.2 O.sub.3 10-30As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-1B.sub.2 O.sub.3 5-15Na.sub.2 O 3-18ZnO 2-10Li.sub.2 O 0-3K.sub.2 O 0-3Al.sub.2 O.sub.3 0-7PbO 0-2MgO 0-3CaO 0-2BaO 0-2SrO 0-2.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7FeO.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5Pr.sub.6 O.sub.11 0-1.______________________________________

2. A glass of claim 1 consisting essentially of, in weight percent

______________________________________SiO.sub.2 45-60Nd.sub.2 O.sub.3 20-30As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-0.5B.sub.2 O.sub.3 5-10Na.sub.2 O 10-15ZnO 1-7Li.sub.2 O 0K.sub.2 O 0Al.sub.2 O.sub.3 0PbO 0MgO 0CaO 0BaO 0SrO 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0Pr.sub.6 O.sub.11 0______________________________________

3. A glass of claim 1 consisting essentially of, in weight percent

______________________________________SiO.sub.2 50-55Nd.sub.2 O.sub.3 22-26As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0.2-0.4B.sub.2 O.sub.3 6-8Na.sub.2 O 11-13ZnO 2-5Li.sub.2 O 0K.sub.2 O 0Al.sub.2 O.sub.3 0PbO 0MgO 0CaO 0BaO 0SrO 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0Pr.sub.6 O.sub.11 0______________________________________

4. A glass of claim 1 having a MgO content.

5. A glass of claim 1 having a TiO.sub.2 content.

6. A glass of claim 1, wherein the amount of ZnO is 2-5 wt.%.

7. A glass of claim 1, wherein the amount of K.sub.2 O is 0.

8. A glass of claim 1, wherein the amount of ZnO is 3-10 wt.%.

9. A glass of claim 1 having a chemically strengthened surface layer prepared by ion exchange.

10. A glass of claim 1 having a chemically strengthened surface layer prepared by ion exchange.

11. A glass of claim 3 having a chemically strengthened surface layer prepared by ion exchange.

12. A glass of claim 8 having a chemically strengthened surface layer prepared by ion exchange.

13. A chemically strengthenable glass consisting essentially of, in weight percent

______________________________________SiO.sub.2 40-60Nd.sub.2 O.sub.3 10-30As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-0.3B.sub.2 O.sub.3 5-15Na.sub.2 O 3-18ZnO 2-10Li.sub.2 O 0-3K.sub.2 O 0-3Al.sub.2 O.sub.3 0-7PbO 0-2MgO 0-3CaO 0-2BaO 0-2SrO 0-2.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5Pr.sub.6 O.sub.11 0-1CeO.sub.2 0.1-2______________________________________

14. A glass of claim 13 consisting essentially of, in weight percent

______________________________________SiO.sub.2 45-60Nd.sub.2 O.sub.3 20-30B.sub.2 O.sub.3 5-10As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0Na.sub.2 O 10-15ZnO 1-7Li.sub.2 O 0K.sub.2 O 0Al.sub.2 O.sub.3 0PbO 0MgO 0CaO 0BaO 0SrO 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0Pr.sub.6 O.sub.11 0CeO.sub.2 0.1-1.______________________________________

15. A glass of claim 13 consisting essentially of, in weight percent

______________________________________SiO.sub.2 50-55Nd.sub.2 O.sub.3 22-26B.sub.2 O.sub.3 6-8As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0Na.sub.2 O 11-13ZnO 2-5Li.sub.2 O 0K.sub.2 O 0Al.sub.2 O.sub.3 0PbO 0MgO 0CaO 0BaO 0SrO 0.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0Pr.sub.6 O.sub.11 0CeO.sub.2 0.4-0.6.______________________________________

16. A glass of claim 13 having a MgO content.

17. A glass of claim 13 having a TiO.sub.2 content.

18. A glass of claim 13, wherein the amount of ZnO is 2-5 wt.%.

19. A glass of claim 13, wherein the amount of K.sub.2 O is 0.

20. A glass of claim 13, wherein the amounts of K.sub.2 O, CaO, BaO, SrO, and PbO are 0.

21. A glass of claim 13 having a chemically strengthened surface layer prepared by ion exchange.

22. A glass of claim 14 having a chemically strengthened surface layer prepared by ion exchange.

23. A glass of claim 15 having a chemically strengthened surface layer prepared by ion exchange.

24. A glass of claim 20 having a chemically strengthened surface layer prepared by ion exchange.

25. A contrast enhancement lens consisting essentially of a glass of claim 9 in the form of a lens.

26. A UV-attenuated lens consisting essentially of a glass of claim 21 in the form of a lens.

27. Sunglasses comprising a lens of claim 25.

28. Sunglasses comprising a lens of claim 26.

29. A glass of claim 1 having a strengthened surface layer prepared by heat treatment of a surface thereof followed by quenching.

30. A glass of claim 13 having a strengthened surface layer prepared by heat treatment of a surface thereof followed by quenching.

31. A CRT filter comprising a glass of claim 9.

32. A CRT filter comprising a glass of claim 21.

33. A high Nd, chemically strengthenable glass consisting essentially of, in mole%:

______________________________________ SiO.sub.2 54-75 Nd.sub.2 O.sub.3 3-6 As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-0.4 B.sub.2 O.sub.3 5-17 Na.sub.2 O 3-18 ZnO 2-10 Li.sub.2 O 0-3 K.sub.2 O 0-3 Al.sub.2 O.sub.3 0-7 PbO 0-2 MgO 0-3 CaO 0-2 BaO 0-2______________________________________

34. A chemically strengthenable glass consisting essentially of, in mole%:

______________________________________SiO.sub.2 54-75Nd.sub.2 O.sub.3 3-6As.sub.2 O.sub.3 /Sb.sub.2 O.sub.3 0-0.4B.sub.2 O.sub.3 5-17Na.sub.2 O 3-18ZnO 2-10Li.sub.2 O 0-3K.sub.2 O 0-3Al.sub.2 O.sub.3 0-7PbO 0-2MgO 0-3CaO 0-2BaO 0-2SrO 0-2.SIGMA.V.sub.2 O.sub.5, Cr.sub.2 O.sub.3, Mn.sub.2 O.sub.3 0-7Fe.sub.2 O.sub.3, CoO, NiO, CuOTiO.sub.2 0-5Pr.sub.6 O.sub.11 0-0.5CeO.sub.2 0.05-1.0.______________________________________

35. A method of chemically strengthening a surface of a silicate glass containing 10-30 wt.% of Nd.sub.2 O.sub.3 and 3-18 wt.% of Na.sub.2 O comprising chemstrengthening such a silicate glass with a composition further consisting essentially of 2-10 wt.% ZnO and less than 2 wt.% of each of K.sub.2 O, PbO, CaO, BaO, and SrO.

36. A glass of claim 1, wherein the amount of Nd is 18-30 wt.%.

37. A glass of claim 1, wherein the amounts of PbO, CaO, BaO and SrO are 0.