| 摘要 |
The present invention relates to an alkali-free glass substrate with a thickness of 0.4 mm or less, which has been reduced in thickness by 5 μm or more by a hydrofluoric acid (HF) etching treatment, in which the alkali-free glass substrate contains an alkali-free glass described below, and the alkali-free glass substrate after reduced in thickness has a specific modulus of 32 MNm/kg or more and a photoelastic constant of 31 nm/MPa/cm or less, the alkali-free glass having a strain point of 710° C. or higher, an average thermal expansion coefficient at 50 to 350° C. of from 30×10−7to 43×10−7/° C., a temperature T2 at which a glass viscosity reaches 102 dPa·s of 1710° C. or lower, a temperature T4 at which the glass viscosity reaches 104 dPa·s of 1320° C. or lower. |
| 主权项 |
1. An alkali-free glass substrate with a thickness of 0.4 mm or less, which has been reduced in thickness by 5 μm or more by a hydrofluoric acid (HF) etching treatment, wherein the alkali-free glass substrate comprises an alkali-free glass described below, and the alkali-free glass substrate after reduced in thickness has a specific modulus of 32 MNm/kg or more and a photoelastic constant of 31 nm/MPa/cm or less, the alkali-free glass having a strain point of 710° C. or higher, a temperature T2 at which a glass viscosity reaches 102 dPa·s of 1710° C. or lower, a temperature T4 at which the glass viscosity reaches 104 dPa·s of 1320° C. or lower, and comprising, indicated by mol % on the basis of oxides,SiO2 66 to 70,Al2O3 12 to 15,B2O3 0 to 1.5,MgOexceeding 9.5 to 13,CaO 4 to 9,SrO0.5 to 4.5,BaO 0 to 1 andZrO2 0 to 2,wherein MgO + CaO + SrO + BaO is from 17 to 21,MgO/(MgO + CaO + SrO + BaO) is 0.40 or more,MgO/(MgO + CaO) is 0.40 or more, andMgO/(MgO + SrO) is 0.60 or more. |
