Low expansion, alkali-free borosilicate glass suitable for photomask applications

Claim 2

An alkali-free glass having a refractive index of at least 1.50, an Abbe number of at least 55, a density of not more than 3.0, and a thermal expansion coefficient of not more than 40.5×10 -7 /°C. over 20°-300° C., and consisting essentially of, in weight percent: ______________________________________ SiO.sub.2 50-60% B.sub.2 O.sub.3 1-6% Al.sub.2 O.sub.3 12-15% MgO 0-2.5% CaO 0-5.1% BaO 9-10% ZnO 12-18% CeO.sub.2 0-5% As.sub.2 O.sub.3 + 0-1.5% Sb.sub.2 O.sub.3 PbO 0-1% ______________________________________ Sum MgO×CaO×BaO ×ZnO=21-33.5.

Claim 3

An alkali-free glass having a refractive index of least 1.50, an Abbe number of at least 55, a density of not more than 3.0, and a thermal expansion coefficient of not more than 40.5×10 -7 /°C. over 20°-300° C, and consisting essentially of, in mole percent: ______________________________________ SiO.sub.2 58-66.5 B.sub.2 O.sub.3 2-5 Al.sub.2 O.sub.3 8-11 MgO 0-4 CaO 0-6.5 BaO 3-5 ZnO 10-16 CeO.sub.2 0-2.5 As.sub.2 O.sub.3 0-0.5 + Sb.sub.2 O.sub.3 PbO 0-0.5 ______________________________________ Sum MgO+CaO+BaO+ZnO=13-31.5.

Claim 4

An alkali-free glass having a refractive index of least 1.50, an Abbe number of at least 55, a density of not more than 3.0, and a thermal expansion coefficient of not more than 40.5×10 -7 /°C. over 20°-300° C, and consisting essentially of, in mole percent: ______________________________________ SiO.sub.2 58-66.5 B.sub.2 O.sub.3 2-5 Al.sub.2 O.sub.3 8-11 MgO 0-4 CaO 0-6.5 BaO 3-5 ZnO 10-16 CeO.sub.2 0-2.5 As.sub.2 O.sub.3 0-0.5 + Sb.sub.2 O.sub.3 PbO 0-0.5 ______________________________________ Sum MgO+CaO+BaO+ZnO=13-31.5.

Claim 5

A glass of claim 1 having the following properties: ______________________________________ refractive index 1.54-1.57 Abbe number 56-59 density (g/cm.sup.3) 2.8-2.9 CTE.sub.20-300° (× 10.sup.-7 °C..sup.-1) 35.5-39.0. ______________________________________

Claim 6

A glass of claim 1 consisting essentially of, in weight percent: ______________________________________ SiO.sub.2 50-56% B.sub.2 O.sub.3 2-3.7% Al.sub.2 O.sub.3 12-15% MgO 1.5-2.5% CaO 2-3% BaO 9-10% ZnO 14-18% CeO.sub.2 0-5% As.sub.2 O.sub.3 0-1.5% + Sb.sub.2 O.sub.3 PbO 0-1% ______________________________________ Sum MgO+CaO+BaO+ZnO=26.5-33.5.

Claim 7

A glass of claim 2 having the following properties: ______________________________________ refractive index 1.54-1.57 Abbe number 56-59 density (g/cm.sup.3) 2.8-2.9 CTE.sub.20-300° (× 10.sup.-7 °C..sup.-1) 35.5-39.0. ______________________________________

Claim 8

A glass of claim 2 consisting essentially of, in mole percent: ______________________________________ SiO.sub.2 58-65 B.sub.2 O.sub.3 2-3.8 Al.sub.2 O.sub.3 8-11 MgO 2.8-4 CaO 2.5-3.5 BaO 3-5 ZnO 10-16 CeO.sub.2 0-2.5 As.sub.2 O.sub.3 0-0.5 + Sb.sub.2 O.sub.3 PbO 0-0.5. ______________________________________ Sum MgO+CaO+BaO+ZnO=23-26.5.

Claim 9

A glass of claim 1 consisting essentially of the following approximate amounts in weight percent: ______________________________________ SiO.sub.2 55.3% B.sub.2 O.sub.3 3.2% Al.sub.2 O.sub.3 12.4% MgO 1.8% CaO 2.5% BaO 9.3% ZnO 14.6% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0.5% PbO 0.5% ______________________________________

Claim 10

A glass of claim 1 consisting essentially of the following approximate amounts in weight percent: ______________________________________ SiO.sub.2 55.6% B.sub.2 O.sub.3 3.2% Al.sub.2 O.sub.3 12.5% MgO 1.8% CaO 2.5% BaO 9.3% ZnO 14.7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0.5% ______________________________________

Claim 11

A glass of claim 1 consisting essentially of the following approximate amounts in weight percent: ______________________________________ SiO.sub.2 50.5% B.sub.2 O.sub.3 3.7% Al.sub.2 O.sub.3 14.5% MgO 2.1% CaO 2.5% BaO 9.2% ZnO 17.1% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0.5% ______________________________________

Claim 12

A glass of claim 1 consisting essentially of the following approximate amounts in weight percent: ______________________________________ SiO.sub.2 50.6% B.sub.2 O.sub.3 3.2% Al.sub.2 O.sub.3 12.5% MgO 1.8% CaO 2.5% BaO 9.3% ZnO 14.7% CeO.sub.2 5.0% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0.5% ______________________________________

Claim 13

A glass of claim 1 consisting essentially of, in weight percent: ______________________________________ SiO.sub.2 50.5-55.6 B.sub.2 O.sub.3 3.2-3.7 Al.sub.2 O.sub.3 12.4-14.5 MgO 1.8-2.1 CaO 2.5-2.55 BaO 9.2-9.3 ZnO 14.6-17.1 As.sub.2 O.sub.3 0.4-0.45 + Sb.sub.2 O.sub.3 PbO 0-0.5. ______________________________________

Claim 14

In a glass photomask, the improvement wherein the compsoition of the glass is that of claim 1.

Claim 15

In a transmissive glass optical element, the improvement wherein the composition of the glass is that of claim 12.

Claim 16

An optical element of claim 13 which is a simple of compound lens or a window.

Claim 17

In an optical element comprising a coated glass substrate, the improvement wherein the composition of the glass substrate is that of claim 1.

Claim 18

In a method of photofabrication comprising irradiating a substrate coated with a photoresist using actinic radiation wherein the radiation is focused onto the substrate through a photomask whereby a desired radiation patter impinges on the substrate, the improvement wherein the photomask consists essentially of a glass composition of claim 1.

Claim 19

In a method of conducting light along a desired optical path comprising at least one transmissive or refractive glass optical element or at least one reflective glass optical element, the improvement wherein at least one of said optical elements comprises a glass of a composition of claim 1.