Alkali-free glass and liquid crystal display panel
To provide an alkali-free glass excellent in the properties for glass substrates to be used for display, excellent in the resistance to reduction, and suitable for forming by a float process. An alkali-free glass consisting essentially of, as represented by mol %: SiO 2 at least 60% and less than 66%, Al 2 O 3 0 to 12%, B 2 O 3 5 to 10%, MgO 0 to 18%, CaO 0 to 18%, SrO 0 to 18%, BaO 0 to 6%, CaO + SrO 10 to 25%, MgO + CaO + SrO + BaO 15.5 to 30% and containing substantially no alkali metal oxide.
1. An alkali-free glass comprising, as represented by mol %:
SiO 2
60 to 64%,
Al 2 O 3
0 to 12%,
B 2 O 3
5 to 10%,
MgO
6 to 18%,
CaO
0 to 18%,
SrO
0 to 18%,
BaO
0 to 2%,
CaO + SrO
12 to 25%,
MgO + CaO + SrO + BaO
18 to 30%,
wherein the alkali-free glass contains substantially no alkali metal oxide and has a temperature T 2 , at which the viscosity becomes log η=2, of at most 1,600° C., and a temperature T 4 , at which the viscosity becomes log η=4, of at most 1,200° C.
2. The alkali-free glass according to claim 1 , wherein B 2 O 3 is from 7 to 10%, CaO+SrO is from 12 to 25% and MgO+CaO+SrO+BaO is from 21 to 30%, as represented by mol %.
3. The alkali-free glass according to claim 1 , which contains substantially no P 2 O 5 , PbO, As 2 O 3 , Sb 2 O 3 or ZnO.
4. The alkali-free glass according to claim 1 , which has a linear expansion coefficient of at most 52×10 −7 /° C. within a range of from 50° C. to 350° C.
5. A liquid crystal display panel, wherein the alkali-free glass as defined in claim 1 is used as at least one substrate among the pair of substrates constituting a cell.
6. The alkali-free glass according to claim 1 , wherein SiO 2 is from 60 to 63%, as represented by mol %.
7. The alkali-free glass according to claim 1 , wherein MgO is from 7 to 18%, as represented by mol %.
8. A process for producing an alkali-free glass, which comprises:
mixing glass components so that the desired composition comprises, as represented by mol %:
SiO 2
60 to 64%,
Al 2 O 3
0 to 12%,
B 2 O 3
5 to 10%,
MgO
6 to 18%,
CaO
0 to 18%,
SrO
0 to 18%,
BaO
0 to 2%,
CaO + SrO
12 to 25%, and
MgO + CaO + SrO + BaO
18 to 30%,
wherein the alkali-free glass contains substantially no alkali metal oxide and has a temperature T 2 , at which the viscosity becomes log η=2, of at most 1,600° C., and a temperature T 4 , at which the viscosity becomes log η=4, of at most 1,200° C.;
heating and melting the mixed glass components within a temperature range of from 1,500° C. to 1,660° C.; and
forming the molten glass by a float process to produce the alkali-free glass.
9. The process for producing an alkali-free glass according to claim 8 , wherein B 2 O 3 is from 7 to 10%, CaO+SrO is from 12 to 25% and MgO+CaO+SrO+BaO is from 21 to 30%, as represented by mol %.
10. The process for producing an alkali-free glass according to claim 8 , wherein at the time of melting the glass components, from 0 to 4 wt % of F, from 0 to 4 wt % of Cl, from 0 to 4 wt % of SO 3 , from 0 to 4 wt % of SnO 2 , from 0 to 4 wt % of TiO 2 , from 0 to 4 wt % of CeO 2 , from 0 to 4 wt % of ZrO 2 , and from 0 to 2 wt % of Fe 2 O 3 , are further added as refining agents so that from 1 ppm to 15 wt % of F+Cl+SO 3 +SnO 2 +TiO 2 +CeO 2 +ZrO 2 +Fe 2 O 3 , based on a total weight of the glass, are present in the glass after the formation.
11. The process for producing an alkali-free glass according to claim 8 , wherein SiO 2 is from 60 to 63%, as represented by mol %.
12. The process for producing an alkali-free glass according to claim 8 , wherein MgO is from 7 to 18%, as represented by mol %.