Transparent laminate which inhibits puncture by projectiles

Abstract

A transparent laminate is provided that includes at least one chemically prestressed pane having a thickness, a compressive stress (CS) of a surface layer, a thickness of the prestressed surface layer and a tensile stress (CT) of an interior portion. The tensile stress (CT) is greater than 0 and is less than the compressive stress divided by 50.

Claims

1. A transparent laminate comprising: at least one chemically prestressed pane, where the at least one chemically prestressed pane has a thickness, a compressive stress (CS) of a prestressed surface layer, a thickness of the prestressed surface layer, and a tensile stress (CT) in an interior, wherein the tensile stress (CT) is greater than 0 and less than the compressive stress (CS) divided by 50, wherein the at least one chemically prestressed pane has a compressive stress (CS) of 400 MPa or more.

2. The transparent laminate according to claim 1, wherein the tensile stress (CT) is less than the compressive stress (CS) divided by 100.

3. The transparent laminate according to claim 1, wherein the tensile stress (CT) is less than the compressive stress (CS) divided by 150.

4. The transparent laminate according to claim 1, wherein the tensile stress (CT) is more than 1 MPa.

5. The transparent laminate according to claim 1, wherein the tensile stress (CT) is more than 2 MPa.

6. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane has a compressive stress (CS) of 700 MPa or more.

7. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane has a compressive stress (CS) of 900 MPa or more.

8. The transparent laminate according to claim 1, wherein the thickness of the at least one chemically prestressed pane is 3 mm or more.

9. The transparent laminate according to claim 1, wherein the thickness of the at least one chemically prestressed pane is 6 mm or more.

10. The transparent laminate according to claim 1, wherein the thickness of the at least one chemically prestressed pane is 9 mm or more.

11. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane is chemically prestressed on an entire outer surface including a circumferential edge.

12. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane comprises two chemically prestressed panes.

13. The transparent laminate according to claim 12, wherein the two chemically prestressed panes are joined to one another by a transparent intermediate layer comprising a pourable resin or a polymer film.

14. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane comprises three or more chemically prestressed panes.

15. The transparent laminate according to claim 14, wherein each of the three or more chemically prestressed panes are joined to one another by a transparent intermediate layer comprising a pourable resin or a polymer film.

16. The transparent laminate according to claim 1, comprising a total laminate thickness of from 30 mm to 200 mm.

17. The transparent laminate according to claim 1, comprising a total laminate thickness of from 50 mm to 150 mm.

18. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane is an aluminosilicate glass pane or a lithium aluminosilicate glass pane.

19. The transparent laminate according to claim 18, wherein the at least one chemically prestressed pane has, in a region which has not been ion-exchanged, the following components in percent by weight (% by weight): TABLE-US-00005 SiO.sub.2 55 to 72, Na.sub.2O 8 to 16, Al.sub.2O.sub.3 11 to 22, K.sub.2O 0.5 to 7, MgO 0 to 9, ZrO.sub.2 0 to 5, ZnO 0 to 4, CaO 0 to 4, and TiO.sub.2 0 to 1.

20. The transparent laminate according to claim 19, wherein the region which has not been ion-exchanged, of the following components in percent by weight (% by weight): TABLE-US-00006 SiO.sub.2 57 to 63, Na.sub.2O 11 to 16, Al.sub.2O.sub.3 15.1 to 18.5, K.sub.2O 2.8 to 5, MgO 3 to 9, ZrO.sub.2 0 to 5, ZnO 0 to 4, CaO 0 to 4, Na.sub.2O + K.sub.2O + MgO + ZnO + CaO 15 to 28, TiO.sub.2 0 to 1, and SnO.sub.2 + Cl + F + SO.sub.3 + CeO.sub.2 0 to 1.5.

21. The transparent laminate according to claim 1, wherein the at least one chemically prestressed pane is a float glass pane having a tin bath side facing an exposed side of the laminate.

22. The transparent laminate according to claim 1, further comprising a transparent polymer layer on a side facing away from an exposed side of the laminate.

23. The transparent laminate according to claim 22, further comprising a glass pane made of a glass having a thickness of from 0.05 to 2 mm arranged on a surface of the polymer layer facing away from the exposed side.

24. The transparent laminate according to claim 23, wherein the glass pane is a chemically prestressed pane.

25. A transparent laminate comprising: a first glass pane having a surface layer and an interior; a second glass pane having a surface layer and an interior, the first and second glass panes being composed of aluminosilicate glass or lithium aluminosilicate glass; and a transparent intermediate layer composed of pourable resin or polymer film joining the first and second glass panes to one another, wherein the first and/or second glass panes are chemically prestressed so that the surface layer has a compressive stress (CS) of at least 400 MPa, the interior has a tensile stress (CT) of more than 1 MPa, and the tensile stress (CT) is less than the compressive stress (CS) divided by 50.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1: Schematic depiction of the stress distribution in a chemically prestressed pane; and

(2) FIG. 2: Laminate according to the invention,

DETAILED DESCRIPTION

(3) FIG. 1 shows, by way of example, the stress profile in a chemically prestressed pane in the direction of the pane thickness. While the pane is under compressive stress in the region of the surface and attains a value CS (Compressive Stress) on the two surfaces, the interior of the pane is under a tensile stress CT (Centre Tension). The depth at which the compressive stress changes into tensile stress is denoted as DOL (Depth of Layer) and can be determined stress-optimetrically. The DOL corresponds approximately to the thickness of the surface layer in which ion exchange has taken place,

(4) FIG. 2 shows the structure of a laminate (10) according to the invention, comprising four chemically prestressed panes (1a, 1b, 1c, 1d), a transparent polymer layer (2) and a thin glass pane (3), with the layers mentioned being joined to one another by means of transparent intermediate layers (4a, 4b, 4c, 4d, 4e) composed of pourable resin or polymer films. A projectile (30) is indicated on the exposed side (11) of the laminate.

Example

(5) The invention is illustrated below with the aid of an example laminate A. A laminate C which has a structure according to the prior art and has the same weight per unit area serves as comparative example.

(6) Laminate A comprises eight panes of chemically prestressed aluminosilicate glass having a thickness of 8.1 mm each and a polycarbonate pane which has a thickness of 3 mm and finishes off the laminate. The aluminosilicate glass panes and the polycarbonate pane are joined to one another by means of a total of 8 organic intermediate layers composed of the commercial polymer Krystalflex PE399 from the manufacturer Huntsman, which each have a thickness of 0.76 mm and only for joining to the polycarbonate pane have a thickness of 1.27 mm. The laminate thus has a total thickness of 74.4 mm. The composite is produced in a commercial autoclave. The laminate has a weight per unit area of 172 kg/m.sup.2. The eight aluminosilicate glass panes are produced in a float process and have the following composition in % by weight:

(7) TABLE-US-00003 SiO.sub.2 60.0 Na.sub.2O 12.5 Al.sub.2O.sub.3 17 K.sub.2O 4 MgO 4 ZrO.sub.2 1.5 SnO.sub.2 0.3 CeO.sub.2 0.3

(8) The chemical hardening of the aluminosilicate glass panes was carried out for a period of 6 hours in a KNO.sub.3 salt solution at a temperature of 420 C., with the panes in each case being preheated and after-heated for about 0.5 hour at a temperature of about 200 C. before and after the salt bath. The thickness of the prestressed layer DOL was determined stress-optometrically and is 48 m, while the compressive stress of the surface CS is about 950 MPa. The tensile stress in the interior of an aluminosilicate glass pane is thus about 5.7 MPa. The aluminosilicate glass panes have a tensile strength in bending of 1.1 GPa determined by a double-ring method based on DIN EN1288-5. The panes are floated and not additionally worked. In particular, no mechanical polishing of the surfaces was carried out.

(9) A conventional laminate which instead of the chemically prestressed panes comprises unprestressed borosilicate glass panes of the type Borofloat 33 and whose further structure is the same as laminate A serves as comparative material laminate C. The thickness of the borosilicate glass panes was modified from 8.1 mm to 9.1 mm so that the laminate C has the same number of panes and the same weight per unit area as laminate A. The total thickness of laminate C is thus 82.4 mm.

(10) To determine the projectile impact resistance, at least 10 sections in each case of the above-described laminate A and the laminate C having dimensions of 100100 mm.sup.2 were produced, with one shot being fired at each section. The specimens were clamped in a circumferential frame.

(11) Testing of the protective effect was carried out by a projectile of the type 7.62 mm51 AP (tungsten carbide core) being fired at the specimen, with the speed of arrival of the projectile being altered and the limit velocity v.sub.L thus being determined. If the projectiles penetrate through the laminate, their exit velocity behind the laminate was determined. The limit velocity v.sub.L is the velocity at which the projectile remains embedded in the laminate with a probability of 50%, i.e. passage through the laminate is prevented to a probability of 50%.

(12) The following values are obtained for the limit velocity v.sub.L

(13) TABLE-US-00004 Laminate A >1080 m/s +/ 30 m/s Laminate C 980 m/s +/ 30 m/s

(14) The laminate according to the invention thus has a significantly higher limit velocity v.sub.L. In addition, the laminate has an 8 mm lower thickness than laminate C.

(15) Due to the test apparatus available, a velocity of 1080 m/s could not be exceeded. All shots at this or lower projectile velocity remained embedded in the laminate A. v.sub.L is thus certainly above this maximum velocity of 1080 m/s, but could not be determined exactly.