Patent ID: 8895463

Claim:
A glass substrate, comprising: a substrate having a surface and comprising a glass material, wherein the glass material has a glass transition temperature of at least 580° C. and an average thermal expansion coefficient of from 70×10 −7 to 100×10 −7 /° C., the substrate comprises at least one of CaO, SrO and BaO such that a ratio of an average total amount in atom % of Ca, Sr and Ba within from 10 to 40 nm in depth from the surface of the substrate to a total amount in atom % of Ca, Sr and Ba at 5,000 nm in depth from the surface of the substrate is at most 0.35, the substrate comprises Na 2 O such that a ratio of an average Na amount in atom % within from 10 to 40 nm in depth from the surface of the substrate after a heat treatment at 600° C. under a N 2 atmosphere for 1 hour to an average Na amount before the heat treatment is at least 1.5, and the substrate comprises, at 5,000 nm or more in depth from the surface of the substrate, as represented by mass % based on oxides, from 53 to 72% of SiO 2 , from 1 to 15% of Al 2 O 3 , from 0.5 to 9% of MgO, from 0.1 to 11% of CaO, from 0 to 11% or SrO, from 0 to 11% or BaO, from 2 to 11% of Na 2 O, from 2 to 21% of K 2 O and from 0 to 10.5% of ZrO 2 , provided that MgO+CaO+SrO+BaO is from 4 to 25%, CaO+SrO+BaO is from 2 to 23%, Na 2 O+K 2 O is from 8 to 22%, and Na 2 O/(CaO+SrO+BaO)≦1.2.