Finish polishing process of the glass substrate, and alkali-free glass substrate which is finish polishing in the process

摘要

The present invention uses a polishing slurry containing cerium oxide as abrasive grains, polishing the main surface of the glass substrate, a final polishing method of a glass substrate, the composition of the glass substrate, the following non an alkali glass, the amount of polishing of the glass substrate when the height of the swell in terms of swell of 20mm pitch of the main surface of the glass substrate is changed from 0.14 m to 0.10 m when the X ( m) , including the step of polishing under the conditions 0.04 / X is 0.12 or more, of the glass substrate on the finish polishing method: be a strain point of 710 or more, the average thermal expansion coefficient of at 50~350 30 10 ^-7 ~43 10 ^-7 a / , the temperature T glass viscosity of 10 ² dPa s ₂ is not more 1710 or less, glass viscosity of 10 ⁴ dPa s to become temperature T ₄ is not more 1320 or less , as represented by mol% based on oxides, SiO ₂ : 66~70, Al ₂ O ₃ : 12~15, B ₂ O ₃ : 0~1.5, MgO: 9.5 ultra 13 or less, CaO: 4~9, SrO: 0.5~4.5, BaO: 0 ~1, ZrO ₂ : 0~2 containing MgO + CaO + SrO + BaO is 17 to 21, and the MgO / (MgO + CaO + SrO + BaO) is 0.40 or more, MgO / (MgO + CaO) is 0.40 or more at is, MgO / (MgO + SrO) is an alkali-free glass, which is a 0.60 or more.