Alkali-free glass
An alkali free glass has an average coefficient of thermal expansion at 50 to 350° C. of 30×10 −7 to 43×10 −7 /° C., a Young's modulus of 88 GPa or more, a strain point of 650 to 725° C., a temperature T 4 at which a viscosity reaches 10 4 dPa·s of 1,290° C. or lower, a glass surface devitrification temperature (T c ) of T 4 +20° C. or lower, and a temperature T 2 at which the viscosity reaches 10 2 dPa·s of 1,680° C. or lower. The alkali free glass contains, as represented by mol % based on oxides, 62 to 67% of SiO 2 , 12.5 to 16.5% of Al 2 O 3 , 0 to 3% of B 2 O 3 , 8 to 13% of MgO, 6 to 12% of CaO, 0.5 to 4% of SrO, and 0 to 0.5% of BaO. MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.
1. An alkali free glass having an average coefficient of thermal expansion at 50 to 350° C. of 30×10 −7 to 43×10 −7 /° C., a Young's modulus of 88 GPa or more, a strain point of 650 to 725° C., a temperature T 4 at which a viscosity reaches 10 4 dPa·s of 1,290° C. or lower, a glass surface devitrification temperature (T c ) of T 4 +20° C. or lower, and a temperature T 2 at which the viscosity reaches 10 2 dPa·s of 1,680° C. or lower, and
comprising, as represented by mol % based on oxides:
62 to 67% of SiO 2 ,
12.5 to 16.5% of Al 2 O 3 ,
0 to 3% of B 2 O 3 ,
8 to 13% of MgO,
6 to 12% of CaO,
0.5 to 4% of SrO, and
0 to 0.5% of BaO,
wherein MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.
2. The alkali free according to claim 1 , having a glass specific elastic modulus of 34 MN·m/kg or higher.
3. The alkali free glass according to claim 1 , having a density of 2.60 g/cm 3 or lower.
4. The alkali free glass according to claim 1 , having a glass surface devitrification viscosity (η c ) of 10 3.8 dPa·s or higher.
5. The alkali free glass according to claim 1 , having, a glass transition temperature of 730 to 790° C.
6. The alkali free glass according to claim 1 , having a value expressed by the following Expression (I) of 4.10 or more:
(7.87[Al 2 O 3 ]−8.5[B 2 O 3 ]+11.35[MgO]+7.09[CaO]+5.52[SrO]−1.45[BaO])/[SiO 2 ] Expression (I).
7. The alkali free glass according to claim 1 , having a value expressed by the following Expression (II) of 0.95 or more:
(−1.02[Al 2 O 3 ]+10.79[B 2 O 3 ]+2.84[MgO]+4.12[CaO]+5.19[SrO]+3.16[BaO])/[SiO 2 ] Expression (II)
8. The alkali free glass according to claim 1 , having a value expressed by the following Expression (III) of 5.5 or less:
(8.9[Al 2 O 3 ]+4.26[B 2 O 3 ]+11.3[MgO]+4.54[CaO]+0.1[SrO]−9.98[BaO])×{1+([MgO]/[CaO]−1) 2 }/[SiO 2 ] Expression (III).
9. The alkali free glass according to claim 1 , comprising 0.5% or lower of SnO 2 as represented by mol % based on oxides.
10. The alkali free glass according to claim 1 , having a β-OH value of 0.05 to 0.5 mm −1 .
11. The alkali free glass according to claim 1 , having a compaction of 100 ppm or lower.
12. The alkali free glass according to claim 1 , having an equivalent cooling rate of 5 to 500° C./min.
13. The alkali free glass according to claim 1 , which is a glass sheet having at least one side of 1,800 mm or longer and a thickness of 0.7 mm or less.
14. The alkali free glass according to claim 13 , which is manufactured by a float process or a fusion process.
15. A display panel comprising the alkali free glass according to claim 1 .
16. A semiconductor device comprising the alkali free glass according to claim 1 .
17. An information recording medium comprising the alkali free glass according to claim 1 .
18. A planar antenna comprising the alkali free glass according to claim 1 .