Thin laminated glass for windscreen
A laminated glazing includes at least one outer glass sheet, an inner glass sheet and a polymeric insert located between the two glass sheets, in which the inner sheet has a thickness of not more than 1.5 mm, the outer glass sheet is a glass sheet of different chemical composition from that of the inner sheet, the difference between the temperatures Tp1 and Tp2 being less than 80° C., the temperature Tp1 being defined as the mean between the upper annealing temperature and the softening point of the outer glass sheet and the temperature Tp2 being defined as the mean between the upper annealing temperature and the softening point of the inner glass sheet.
1. A laminated glazing comprising at least one outer glass sheet, an inner glass sheet and a polymeric insert located between the outer and inner glass sheets, in which
the inner glass sheet has a thickness of not more than 1.5 mm,
the outer glass sheet is a non-chemically reinforced glass sheet of different chemical composition from that of the inner glass sheet,
a difference between the temperatures Tp1 and Tp2 being less than 80° C., with temperature Tp1 being greater than temperature Tp2,
wherein the temperature Tp1 is the average of the upper annealing temperature and the softening point of the outer glass sheet, and wherein the temperature Tp2 is the average of the upper annealing temperature and the softening point of the inner glass sheet, a general formula defining the temperature Tp being
Tp =( T softening +T annealing )/2
wherein the upper annealing temperature corresponding to the temperature at which a viscosity of a glass material is 10 13 poises and the softening point corresponding to the temperature at which a viscosity of a glass material is 10 7.6 poises,
wherein the laminated glazing is a bent glazing and constitutes a motor vehicle windshield,
wherein a thickness of the outer glass sheet is greater than the thickness of the inner glass sheet, and
wherein the polymeric insert has a thickness from 500 μm to 4 mm.
2. The glazing as claimed in claim 1 , wherein the difference between the temperatures Tp1 and Tp2 is less than 70° C.
3. The glazing as claimed in claim 1 , wherein the outer glass sheet has a thickness of not more than 2.1 mm.
4. The glazing as claimed in claim 1 , wherein the polymeric insert comprises one or more layers of thermoplastic chosen from polyurethane, polycarbonate, polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and ethylene-vinyl acetate (EVA) or an ionomeric resin.
5. The glazing as claimed in claim 4 , wherein the polymeric insert comprises at least one layer made of polyvinyl butyral.
6. The glazing as claimed in claim 1 , wherein the outer glass sheet has a chemical composition of a borosilicate glass.
7. The glazing as claimed in claim 6 , wherein the outer glass sheet comprises
SiO 2
75-85%,
Al 2 O 3
2-3%,
B 2 O 3
10-15%,
Na 2 O + K 2 O
3-7%.
8. The glazing as claimed in claim 1 , wherein the outer glass sheet has a chemical composition of a sodium aluminosilicate glass.
9. The glazing as claimed in claim 8 , wherein the outer glass sheet comprises
SiO 2
55-71%,
Al 2 O 3
2-15%
Na 2 O
9-18%
MgO
2-11%
K 2 O
1-15%
B 2 O 3
0-5%,
CaO
0-5%
SnO 2
0-5%.
10. The glazing as claimed in claim 9 , wherein the outer glass sheet comprises 4-15% of Al 2 O 3 .
11. The glazing as claimed in claim 1 , wherein the inner glass sheet has a thickness of not more than 1.1 mm.
12. The glazing as claimed in claim 1 , wherein the inner glass sheet has a composition of a silicon-sodium-calcium glass.
13. The glazing as claimed in claim 2 , wherein the difference between the temperatures Tp1 and Tp2 is less than 60° C.
14. The glazing as claimed in claim 3 , wherein the outer glass sheet has a thickness of not more than 1.6 mm.
15. The glazing as claimed in claim 11 , wherein the inner glass sheet has a thickness of less than 1 mm.
16. The glazing as claimed in claim 1 , wherein the polymeric insert has a thickness from 760 μm to 4 mm.