초록 ▼

Glass-ceramics include SiO2, Al2O3 and Li2O on oxide basis. In the glass-ceramics, total amount in mass % of SiO2 and Al2O3 is less than 77% and Li2O/(SiO2+Al2O3) which is the ratio in mass % of the amount of Li2O to the total amount of SiO2 and Al2O3 is 0.064 or over. The glass-ceramics include at

Glass-ceramics include SiO2, Al2O3 and Li2O on oxide basis. In the glass-ceramics, total amount in mass % of SiO2 and Al2O3 is less than 77% and Li2O/(SiO2+Al2O3) which is the ratio in mass % of the amount of Li2O to the total amount of SiO2 and Al2O3 is 0.064 or over. The glass-ceramics include at least one crystal phase selected from the group consisting of β-quartz, β-quartz solid solution, β-eucryptite, β-eucryptite solid solution, β-spodumene and β-spodumene solid solution.

대표청구항 ▼

1. Glass-ceramics comprising SiO2, Al2O3 and Li2O on oxide basis, wherein the glass-ceramics contains in mass % SiO240-60%,MgO 0-9%,TiO2 0-4.5%, andone or both of K2O 1-7% and Na2O 1-7%,wherein total amount in mass % of SiO2 and Al2O3 is less than 77%, andLi2O/(SiO2+Al2O3) which is the ratio in mass

1. Glass-ceramics comprising SiO2, Al2O3 and Li2O on oxide basis, wherein the glass-ceramics contains in mass % SiO240-60%,MgO 0-9%,TiO2 0-4.5%, andone or both of K2O 1-7% and Na2O 1-7%,wherein total amount in mass % of SiO2 and Al2O3 is less than 77%, andLi2O/(SiO2+Al2O3) which is the ratio in mass % of the amount of Li2O to the total amount of SiO2 and Al2O3 being 0.064 or over, andthe glass-ceramics comprises at least one crystal phase selected from the group consisting of β-quartz, β-quartz solid solution, β-eucryptite, β-eucryptite solid solution, β-spodumene and β-spodumene solid solution. 2. Glass-ceramics as defined in claim 1 wherein the glass-ceramics is capable of having logarithm (logη) of viscosity η(dPa·s) of 3.0 or below when the glass-ceramics are heated to 1400° C. 3. Glass-ceramics as defined in claim 1 wherein average coefficient of linear thermal expansion within temperature range between 25° C. and 100° C. is −10 to 50 (10−7° C.−1). 4. Glass-ceramics as defined in claim 1 wherein average crystal grain diameter of the crystal phase is 1 μm or below. 5. Glass-ceramics as defined in claim 1 having Young's modulus of 90 GPa or over. 6. Glass-ceramics as defined in claim 1 having ratio E/ρ of Young's modulus E to specific gravity ρ of 32 or over. 7. Glass-ceramics as defined in claim 1 comprising, in mass % on oxide basis: Li2O 4-15% andAl2O315-30%. 8. Glass-ceramics as defined in claim 7 further comprising, in mass % on oxide basis, one or more components selected from: CaO0-10%,ZnO0-10%,BaO 0-7%,P2O50-15%,ZrO2 0-5%,B2O3 0-5%,one or more oxides selected from Gd2O3, La2O3, Y2O3 and Ga2O3 in total amount of 0-10%, andone or both of Sb2O3 and As2O3 in total amount of 0-2%. 9. A substrate of a magnetic information storage medium using the glass-ceramics as defined in claim 1. 10. A substrate of a magnetic information storage medium having a compressive stress layer on the substrate as defined in claim 9. 11. A substrate as defined in claim 10 wherein the compressive stress layer is formed by substituting by a cation having a larger ionic radius than ions contained in a surface of the substrate. 12. A substrate as defined in claim 10 wherein the compressive stress layer is formed by heating and subsequent quenching of the substrate. 13. A substrate as defined in claim 9 having surface roughness Ra (arithmetic mean roughness) of 3A or below. 14. A magnetic information storage medium using the substrate of a magnetic information storage medium as defined in claim 9.