Non-alkali glass, and process for production of non-alkali glass
View Patent ↗The present invention relates to an alkali-free glass having a strain point of 735° C. or higher, an average thermal expansion coefficient at from 50 to 350° C. of from 30×10 −7 to 40×10 −7 /° C., a temperature T 2 at which a glass viscosity is 10 2 dPa·s of 1,710° C. or lower, a temperature T 4 at which a glass viscosity is 10 4 dPa·s of 1,340° C. or lower, and a devitrification temperature of 1,330° C. or lower, the alkali-free glass including, in terms of mol % on the basis of oxides: SiO 2 66 to 69, Al 2 O 3 12 to 15, B 2 O 3 0 to 1.5, MgO 6 to 9.5, CaO 7 to 9, SrO 0.5 to 3, BaO 0 to 1, and ZrO 2 0 to 2, in which MgO+CaO+SrO+BaO is from 16 to 18.2, MgO/(MgO+CaO+SrO+BaO) is 0.35 or more, MgO/(MgO+CaO) is 0.40 or more and less than 0.52, and MgO/(MgO+SrO) is 0.45 or more.
1. An alkali-free glass comprising, in terms of mol % on the basis of oxides:
SiO 2
66 to 69,
Al 2 O 3
12 to 15,
B 2 O 3
0 to 1.5,
MgO
6 to 9.5,
CaO
7 to 9,
SrO
0.5 to 3,
BaO
0 to 1, and
ZrO 2
0 to 2,
wherein MgO+CaO+SrO+BaO is from 16 to 18.2,
MgO/(MgO+CaO+SrO+BaO) is 0.35 or more, and
MgO/(MgO+CaO) is 0.40 or more and less than 0.52,
wherein the alkali-free glass has a strain point of 735° C. or higher, an average thermal expansion coefficient at from 50 to 350° C. of from 30×10 −7 to 40×10 −7 /° C., a temperature T 2 at which a glass viscosity is 10 2 dPa·s of 1,710° C. or lower, a temperature T 4 at which a glass viscosity is 10 4 dPa·s of 1,340° C. or lower, and a devitrification temperature of 1,330° C. or lower.
2. The alkali-free glass according to claim 1 , wherein the alkali-free glass does not substantially contain B 2 O 3 .
3. The alkali-free glass according to claim 1 , wherein the alkali-free glass does not substantially contain BaO.
4. The alkali-free glass according to claim 1 , wherein MgO+CaO+SrO+BaO is from 17 to 18, in terms of mol % on the basis of oxides.
5. The alkali-free glass according to claim 1 , wherein the alkali-free glass does not substantially contain P 2 O 5 .
6. The alkali-free glass according to claim 1 , wherein the alkali-free glass does not substantially contain any of PbO, As 2 O 3 , and Sb 2 O 3 .
7. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise a silica sand, in which a median diameter D 50 is from 20 to 27 μm, a proportion of particles having a particle size of 2 μm or less is 0.3 vol % or less, and a proportion of particles having a particle size of 100 μm or more is 2.5 vol % or less, as a silicon source of SiO 2 ; and
melting the raw materials such that the alkali-free glass of claim 1 is produced.
8. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise an alkaline earth metal source of MgO, CaO, SrO and BaO, the alkaline earth metal source comprising a hydroxide of an alkaline earth metal in a content of from 15 to 100 mol % of 100 mol % of the alkaline earth metal source in terms of MO, wherein M is an alkaline earth metal element; and
melting the raw materials such that the alkali-free glass of claim 1 is produced.
9. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise:
a silica sand, in which a median diameter D 50 is from 20 to 27 μm, a proportion of particles having a particle size of 2 μm or less is 0.3 vol % or less, and a proportion of particles having a particle size of 100 μm or more is 2.5 vol % or less, as a silicon source of SiO 2 ; and
an alkaline earth metal source of MgO, CaO, SrO and BaO, the alkaline earth metal source comprising a hydroxide of an alkaline earth metal in a content of from 15 to 100 mol % of 100 mol % of the alkaline earth metal source in terms of MO, wherein M is an alkaline earth metal element; and
melting the raw materials such that the alkali-free glass of claim 1 is produced.
10. The alkali-free glass according to claim 1 , wherein the alkali-free glass comprises, in terms of mol % on the basis of oxides:
SiO 2
67 to 69,
Al 2 O 3
13.5 to 14.5,
B 2 O 3
0 to 1,
MgO
7 to 8.5,
CaO
7.5 to 8.5,
SrO
1 to 3, and
BaO
0 to 1,
wherein the alkali-free glass does not substantially contain ZrO 2 , and
wherein the alkali-free glass has the strain point of 735° C. or higher, (the temperature T 4 − the devitrification temperature of the glass)≧0° C., and Young's modulus of 84 GPa or more.
11. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise a silica sand, in which a median diameter D 50 is from 20 to 27 μm, a proportion of particles having a particle size of 2 μm or less is 0.3 vol % or less, and a proportion of particles having a particle size of 100 μm or more is 2.5 vol % or less, as a silicon source of SiO 2 ; and
melting the raw materials such that the alkali-free glass of claim 10 is produced.
12. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise an alkaline earth metal source of MgO, CaO, SrO and BaO, the alkaline earth metal source comprising a hydroxide of an alkaline earth metal in a content of from 15 to 100 mol % of 100 mol % of the alkaline earth metal source in terms of MO, wherein M is an alkaline earth metal element; and
melting the raw materials such that the alkali-free glass of claim 10 is produced.
13. A method for producing an alkali-free glass, comprising:
mixing raw materials which comprise:
a silica sand, in which a median diameter D 50 is from 20 to 27 μm, a proportion of particles having a particle size of 2 μm or less is 0.3 vol % or less, and a proportion of particles having a particle size of 100 μm or more is 2.5 vol % or less, as a silicon source of SiO 2 ; and
an alkaline earth metal source of MgO, CaO, SrO and BaO, the alkaline earth metal source comprising a hydroxide of an alkaline earth metal in a content of from 15 to 100 mol % of 100 mol % of the alkaline earth metal source in terms of MO, wherein M is an alkaline earth metal element; and
melting the raw materials such that the alkali-free glass of claim 10 is produced.