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

• US 4,554,259 A
• Filed: 05/08/1984
• Issued: 11/19/1985
• Est. Priority Date: 05/08/1984
• Status: Expired due to Term

• Current Assignee: Schott Glass Technologies, Inc.
• Original Assignee: Schott Glass Technologies, Inc.
• Inventors: Mader, Karl-Heinz, Franklin, Brian
• Primary Examiner(s): McCarthy, Helen M.
• Application Number:
  US06/608,304
• Time in Patent Office: 560 Days
• Field of Search: 501/903, 501/67, 501/64, 501/61, 501/62, 430/5
• US Class Current: 501/67
• CPC Class Codes: C03C 3/093 containing zinc or zirconium
• CPC Class Codes: Y10S 501/903 having refractive index less than 1.8 and ABBE number less than 70

Abstract

Alkali-free borosilicate glass have been developed having coefficients of thermal expansion (+20° C. to +200° C.) below 40.5×10^-7, densities less than 3.0 g/cm³ and good visible and UV transmission, and can be produced by conventional continuous melting techniques. These glasses are particularly suitable for photomask, photovoltaic and mirror substrate applications. Their compositions comprise, in weight percent:

______________________________________                                    

SiO₂ 50-60% B₂ O₃ 1-6% Al₂ O₃ 12-15% MgO 0-2.5% CaO 0-5.1% BaO 9-10% ZnO 12-18% CeO₂ 0-5% As₂ O₃ + 0-1.5% Sb₂ O₃ PbO 0-1% ______________________________________

Sum MgO+CaO+BaO+ZnO=21-33.5.

Claims

1. 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;

space="preserve" listing-type="tabular">______________________________________ 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.

3. A glass of claim 1 having the following properties:

space="preserve" listing-type="tabular">______________________________________ 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. ______________________________________

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

space="preserve" listing-type="tabular">______________________________________ 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.

7. A glass of claim 1 consisting essentially of the following approximate amounts in weight percent:

space="preserve" listing-type="tabular">______________________________________ 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% ______________________________________

8. A glass of claim 1 consisting essentially of the following approximate amounts in weight percent:

space="preserve" listing-type="tabular">______________________________________ 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% ______________________________________

9. A glass of claim 1 consisting essentially of the following approximate amounts in weight percent:

space="preserve" listing-type="tabular">______________________________________ 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% ______________________________________

10. A glass of claim 1 consisting essentially of the following approximate amounts in weight percent:

space="preserve" listing-type="tabular">______________________________________ 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% ______________________________________

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

space="preserve" listing-type="tabular">______________________________________ 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. ______________________________________

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

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

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

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

16. 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.

17. 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.

2. 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;

space="preserve" listing-type="tabular">______________________________________ 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.

5. A glass of claim 2 having the following properties:

space="preserve" listing-type="tabular">______________________________________ 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. ______________________________________

6. A glass of claim 2 consisting essentially of, in mole percent:

space="preserve" listing-type="tabular">______________________________________ 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.