Alkali-free glass substrate

• US 5,851,939 A
• Filed: 05/23/1997
• Issued: 12/22/1998
• Est. Priority Date: 09/28/1995
• Status: Expired due to Term

• Current Assignee: Nippon Electric Glass Company Limited
• Original Assignee: Nippon Electric Glass Company Limited
• Inventors: Miwa, Shinkichi
• Primary Examiner(s): MARCHESCHI, MICHAEL A
• Application Number:
  US08/849,043
• Time in Patent Office: 578 Days
• Field of Search: 501/66, 501/67, 501/69, 501/70, 501/72
• US Class Current: 501/70
• CPC Class Codes: C03C 3/091 containing aluminium

Abstract

In order to provide an alkali-free glass substrate which contains substantially no alkali metal oxide, which has chemical resistance, a high strain point, excellent meltability, and devitrification resistance, the alkali-free glass substrate contains substantially no alkali metal oxide and essentially consists, by weight, of 58.0-68.0% SiO₂, 10.0-25.0% Al₂ O₃, 3.0-15.0% B₂ O₃, 0-2.9% MgO, 0-8.0% CaO, 0.1-5.0% BaO, 0.1-10.0% SrO, 0-5.0% ZnO, 0-5.0% ZrO₂, and 0-5.0% TiO₂.

Claims

1. An alkali-free glass substrate consisting essentially of, by weight, 58.0-68.0% SiO₂, 10.0-25.0% Al₂ O₃, 3.0-15.0% B₂ O₃, 0-2.9% MgO, 0-8.0% CaO, 0.1-5.0% BaO, 0.1-10.0% SrO, 0-5.0% ZnO, 5.0-20.0% MgO+CaO+SrO+BaO+ZnO, 0-5.0% ZrO₂, and 0-5.0% TiO₂, said substrate being essentially free of alkali metal oxide, having a density not exceeding 2.55 g/cm³, and a chemical resistance so that the glass surface does not change after the glass is immersed for 30 minutes in a buffered hydrofluoric acid solution held at 20°

C., said buffered hydrofluoric acid solution comprising, by weight, 38.7% ammonium fluoride and 1.6% hydrofluoric acid.