Patent ID: 9708211
Date: 2017-07-18
CPC Classifications: C03C

Claim:
1. An alkali-free glass substrate, having a strain point of 680° C. or higher, a Young's modulus of 78 GPa or greater, an UV transmittance at a wavelength of 300 nm of from 40% to 85% in terms of 0.5 mm thickness, an in-plane distribution of the transmittance at a wavelength of 300 nm in a G6-sized substrate of 1% or less in terms of 0.5 mm thickness, an average cooling rate around the glass transition point obtained according to a rate cooling method of 400° C./min or lower, and an in-plane distribution of the average cooling rate of 40° C./min or less, and comprising, on a mass percentage basis in terms of oxides: SiO Al B MgO 0 to 10; CaO 0 to 14.5; SrO 0 to 24; BaO 0 to 20; ZrO SnO Fe wherein MgO+CaO+SrO BaO is from 8 to 29.5, and wherein the alkali-free glass substrate is obtained by managing temperature conditions at the time of forming and annealing such that an average cooling rate around the glass transition point obtained according to a rate cooling method is 400° C./min or lower, an in-plane distribution of the average cooling rate is 40° C./min or less, and an in-plane distribution of the UV transmittance at a wavelength of 300 nm in a G6-sized substrate is 1% or less in terms of 0.5 mm thickness.