Patent ID: 8324124

Claim:
A process for producing a glass substrate, which comprises forming molten glass obtained by melting raw materials into a glass ribbon in a float bath, annealing the glass ribbon by a cooling apparatus and cutting the glass ribbon to form the glass substrate, wherein a hydrogen concentration in an atmosphere of the float bath exceeds 3%, and a glass retention time in the float bath is from 4 to 15 minutes, wherein the glass substrate has a composition comprising, as represented by mass percentage based on oxides, SiO 2 55 to 65%, Al 2 O 3 4 to 8%, MgO 6 to 9%, CaO 0.1 to 5%, SrO 0.5 to 6%, BaO 0 to 2%, MgO + CaO + SrO + BaO 6.6 to 19%, Na 2 O 0 to 5%, K 2 O 9.5 to 21%, Na 2 O + K 2 O 10 to 22%, ZrO 2 0.5 to 5%, Fe 2 O 3 0.06 to 0.15%, where the composition has a specific gravity of at most 2.7, an average thermal expansion coefficient from 50 to 350° C. of from 80×10 −7 /° C. to 90×10 −7 /° C., and a glass transition temperature of at least 640° C., and wherein when a viscosity is η, the temperature at which log η=2 is satisfied is at most 1,550° C., and a yellow coloring b* on a surface of the glass is at most 8 after a silver paste is applied on the glass surface, followed by firing, and then the silver paste is removed.