Patent ID: 8281618

Claim:
A process for producing an alkali-free glass substrate comprising melting a glass raw material and forming a glass sheet by an overflow down draw method, wherein, in a cooling step during said forming, an average cooling rate in a temperature range from an annealing point to a temperature lowered by 100° C. from the annealing temperature is 300° C./min or more, and wherein the alkali-free glass substrate has an absolute value of a thermal shrinkage of 50 ppm or more when the alkali-free glass substrate is heated at a rate of 10° C./min from a room temperature, kept at a holding temperature of 450° C. for 10 hours, and then cooled at a rate of 10° C./min, wherein the produced alkali-free glass substrate comprises, by weight %, 50 to 70% of SiO 2 , 1 to 20% of Al 2 O 3 , 0 to 15% of B 2 O 3 to 30% of MgO, 0 to 30% of CaO, 0 to 30% of SrO and 0 to 30% of BaO.