Thin laminated glass

Abstract

A laminated glazing includes at least one outer glass sheet and a polymeric sheet, in which the outer glass sheet has a thickness of not more than 2 mm and a coefficient of thermal expansion of less than 7010.sup.7 K.sup.1.

Claims

1. A laminated windshield of a vehicle, the laminated windshield being resistant to projections of gravel and comprising: at least one outer glass sheet for facing an exterior of the vehicle, at least one inner glass sheet for facing an interior of the vehicle, the inner glass sheet having a thickness of not more than 1.1 mm, and a polymeric sheet located between the inner and outer glass sheets, wherein the inner glass sheet is thinner than the outer glass sheet, wherein the outer glass sheet has a thickness of not more than 1.6 mm and a coefficient of thermal expansion of less than 5010.sup.7 K.sup.1, wherein the inner glass sheet has a chemical composition of a soda-lime glass, and wherein the laminated windshield is a bent windshield for being mounted to the vehicle such that the inner glass sheet is more proximal to the interior of the vehicle than the outer glass sheet is, and wherein the polymeric sheet has a thickness from 500 m to 4 mm.

2. The laminated windshield as claimed in claim 1, wherein the outer glass sheet has a chemical composition of a borosilicate glass.

3. The laminated windshield as claimed in claim 2, wherein the outer glass sheet comprises TABLE-US-00006 SiO.sub.2 75-85%, Al.sub.2O.sub.3 2-3%, B.sub.2O.sub.3 10-15%, Na.sub.2O + K.sub.2O 3-7%.

4. The laminated windshield as claimed in claim 2, wherein the outer glass sheet comprises TABLE-US-00007 SiO.sub.2 60-65%, Al.sub.2O.sub.3 13-18%, B.sub.2O.sub.3 8-14%, CaO + MgO + SrO 6-10%.

5. The laminated windshield as claimed in claim 1, wherein the outer glass sheet has a chemical composition of a lithium aluminosilicate glass and comprises TABLE-US-00008 SiO.sub.2 52-75%, Al.sub.2O.sub.3 15-27%, Li.sub.2O 2-10%, Na.sub.2O 0-1%, K.sub.2O 0-5%, CaO 0-0.5%,.sup. ZnO 0-5%, MgO 0-5%, BaO 0-5%, SrO 0-3%, TiO.sub.2 0-6%, ZrO.sub.2 0-3%, P.sub.2O.sub.5 0-8%.

6. The laminated windshield as claimed in claim 1, wherein the polymeric sheet comprises one or more layers of thermoplastic material chosen from polyurethane, polycarbonate, polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and ethylene-vinyl acetate (EVA) or an ionomeric resin.

7. The laminated windshield as claimed in claim 1, wherein the polymeric sheet comprises at least one layer of PVB.

8. The laminated windshield as claimed in claim 1, wherein the outer glass sheet is a sheet that is not chemically or thermally reinforced.

9. The laminated windshield as claimed in claim 1, wherein the laminated windshield constitutes a motor vehicle laminated windshield.

10. The laminated windshield as claimed in claim 1, wherein the laminated windshield constitutes a laminated windshield for helicopters.

11. The laminated windshield as claimed in claim 1, wherein the inner glass sheet has a thickness of less than 1 mm.

12. The laminated windshield as claimed 1, wherein the outer glass sheet has a thickness of not more than 1.1 mm.

13. The laminated windshield as claim 1, wherein a total thickness of the inner glass sheet, the outer glass sheet and the polymeric sheet is less than 4.5 mm.

14. The laminated windshield as claim 13, wherein a total thickness of the inner glass sheet, the outer glass sheet and the polymeric sheet is less than 4 mm.

15. The glazing as claimed in claim 1, wherein the polymeric sheet has a thickness from 760 m to 4 mm.

16. A bent laminated windshield of a vehicle, the bent laminated windshield being resistant to projections of gravel and comprising: at least one bent outer glass sheet with a convex outer surface for facing an exterior of the vehicle, at least one bent inner glass sheet with a concave inner surface for facing an interior of the vehicle, the bent inner glass sheet having a thickness of not more than 1.1 mm, and a polymeric sheet located between the inner and outer glass sheets, wherein the bent inner glass sheet is thinner than the bent outer glass sheet, wherein the bent outer glass sheet has a thickness of not more than 1.6 mm and a coefficient of thermal expansion of less than 5010.sup.7 K.sup.1, wherein the bent inner glass sheet has a chemical composition of a soda-lime glass, wherein the bent laminated windshield is for being mounted to the vehicle such that the bent inner glass sheet is more proximal to the interior of the vehicle than the bent outer glass sheet is, and wherein the polymeric sheet has a thickness from 500 m to 4 mm.

17. The bent laminated windshield as claimed in claim 16, wherein the bent outer glass sheet has a chemical composition of a borosilicate glass.

18. The bent laminated windshield as claimed in claim 17, wherein the bent outer glass sheet comprises TABLE-US-00009 SiO.sub.2 75-85%, Al.sub.2O.sub.3 2-3%, B.sub.2O.sub.3 10-15%, Na.sub.2O + K.sub.2O 3-7%.

19. The bent laminated windshield as claimed in claim 16, wherein the polymeric sheet has a thickness from 760 m to 4 mm.

20. A vehicle comprising a bent laminated windshield, the bent laminated windshield being resistant to projections of gravel and comprising: at least one outer glass sheet for facing an exterior of the vehicle, at least one inner glass sheet for facing an interior of the vehicle, the inner glass sheet having a thickness of not more than 1.1 mm, and a polymeric sheet located between the inner and outer glass sheets, wherein the inner glass sheet is thinner than the outer glass sheet, wherein the outer glass sheet has a thickness of not more than 1.6 mm and a coefficient of thermal expansion of less than 5010.sup.7 K.sup.1, wherein the inner glass sheet has a chemical composition of a soda-lime glass, wherein the bent laminated windshield is mounted to the vehicle such that the inner glass sheet is more proximal to the interior of the vehicle than the outer glass sheet is, and wherein the polymeric sheet has a thickness from 500 m to 4 mm.

21. The vehicle as claimed in claim 20, wherein the outer glass sheet has a chemical composition of a borosilicate glass.

22. The vehicle as claimed in claim 21, wherein the outer glass sheet comprises TABLE-US-00010 SiO.sub.2 75-85%, Al.sub.2O.sub.3 2-3%, B.sub.2O.sub.3 10-15%, Na.sub.2O + K.sub.2O 3-7%.

23. The vehicle as claimed in claim 20, wherein the polymeric sheet has a thickness from 760 m to 4 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the results of the indentation test (Sarbacane test) for various laminated glasses according to Example 1, and

(2) FIG. 2 shows the results of the indentation test (Sarbacane test) for various laminated glasses according to Example 2.

(3) The examples below illustrate the invention without limiting its scope.

(4) The indentation test (<<Sarbacane<<test) is performed on four different thin laminated glasses consisting of: an inner glass sheet of silicon-sodium-calcium type, of composition C1 given in Table 1 below (ordinary transparent clear glass), a standard polymeric insert made of PVB with a thickness of 0.76 mm, an outer glass sheet of composition C2 to C5 given in Table 1 below.

(5) Composition C1 is a silicon-sodium-calcium glass. Compositions C2 to C4 make it possible to obtain laminated glazings according to the present invention. Compositions C2 and C3 are glasses of borosilicate type. Composition C4 is a glass of lithium aluminosilicate type.

(6) Composition C5 is a glass of sodium aluminosilicate type, given for comparative purposes.

(7) TABLE-US-00004 TABLE 1 composition of the glasses weight % C1 C2 C3 C4 C5 SiO.sub.2 71.1 80.5 63.6 68.2 60.7 Al.sub.2O.sub.3 0.65 2.5 16 18.95 7.7 B.sub.2O.sub.3 12.95 10.7 Na.sub.2O 13.8 3.42 13.1 K.sub.2O 0.25 0.63 9.55 Li.sub.2O 3.45 CaO 8.75 7.8 MgO 4 0.1 1.2 8.4 SrO 0.7 ZnO 1.62 TiO.sub.2 2.58 ZrO.sub.2 1.68

(8) The coefficients of thermal expansion of the glasses of compositions C1 to C5 are given in Table 2.

(9) TABLE-US-00005 C1 C2 C3 C4 C5 CTE (10.sup.7/K) 89 32 32 41 108

(10) The outer glass sheet is the sheet directly subjected to the impact of the diamond-tipped indenter.

(11) The first height at which a crack appears on the outer sheet is measured for each laminated glazing tested.

EXAMPLE 1

(12) Laminated glasses consisting of an inner glass sheet of composition C1 0.55 mm thick, a standard PVB insert 0.76 mm thick and outer glass sheets of composition C1, C2, C4 and C5 1.1 mm thick are subjected to the indentation test (Sarbacane test). The results are given in FIG. 1 in which is shown the drop height of the Vickers indenter at which the first star-shaped cracks appear according to the indentation test described previously. The laminated glazings tested are noted in the following manner: composition of the outer glass sheet/nature of the polymeric sheet/composition of the inner glass sheet. Thus, the laminated glazing C2/PVB/C1 corresponds to an outer sheet made of glass of borosilicate type of composition C2, a PVB insert and an inner sheet made of silicon-sodium-calcium glass of composition C1.

(13) The laminated glazings C1/PVB/C1 and C5/PVB/C1 are not in accordance with the invention and are given for comparative purposes.

(14) It is noted that the glazings according to the invention are those that have the best mechanical strengths.

EXAMPLE 2

(15) Laminated glasses consisting of an inner glass sheet of composition C1 0.7 mm thick, a standard PVB insert 0.76 mm thick and glass sheets of composition C1, C3 and C4 0.7 mm thick are subjected to the indentation test. The test results are given in FIG. 2.

(16) The laminated glazing C1/PVB/C1 is not in accordance with the invention and is given for comparative purposes.

(17) It is noted that the laminated glazing C3/PVB/C1 according to the invention has very good mechanical strength, despite a low sheet thickness (the total thickness of the laminated glazing is 2.16 mm).