COMPOSITE GLASS PANE

Abstract

A laminated glass pane is provided that includes a first glass sheet, a polymeric layer having a thickness between at least 0.5 mm and at most 1.7 mm, and a second inner glass sheet which has a thickness of at least 0.3 mm and at most 1.5 mm and is made of a lithium aluminum silicate glass. The polymeric layer is disposed between the at least two glass sheets. Furthermore, the glasses of the first and the second glass sheets are matched so that the temperatures at which the two glasses of the first and second glass sheets have the same viscosity in the viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s differ from each other only by a maximum of 50 C.

Claims

1. A laminated glass pane, comprising: a first glass sheet; a second glass sheet having a thickness between at least 0.3 mm and at most 1.5 mm, the second glass sheet being made of a lithium aluminum silicate glass; and a polymeric layer having a thickness between at least 0.5 mm and at most 1.7 mm, the polymeric layer between and bonding the first and second glass sheets to one another, wherein the first and second glass sheets comprise glasses that, in a viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s, are matched so that temperatures at which the first and second glass sheets have a same viscosity only differ from each other by not more than 50 C.

2. The laminated glass pane of claim 1, wherein the temperatures differ by not more than 10 C.

3. The laminated glass pane of claim 1, wherein the lithium aluminum silicate glass exhibits a Young's modulus of at least 80 GPa.

4. The laminated glass pane of claim 3, wherein the Young's modulus is at least 84 GPa.

5. The laminated glass pane of claim 1, wherein the second glass sheet is a chemically toughened glass sheet having a compressive stress zone with a depth of at least 40 m and a compressive stress of at least 150 MPa and at most 900 MPa.

6. The laminated glass pane of claim 5, wherein the compressive stress is at most 600 MPa.

7. The laminated glass pane of claim 5, wherein the depth is at least 80 rn.

8. The laminated glass pane of claim 5, wherein the second glass sheet comprises surfaces that are enriched in sodium and depleted of lithium in a region of the compressive stress zone compared to the bulk of the second glass sheet.

9. The laminated glass pane of claim 1, further comprising a curvature such that an outwardly facing side of the second glass sheet is curved concavely.

10. The laminated glass pane of claim 1, further comprising a uniaxial curve or a biaxially curve.

11. The laminated glass pane of claim 10, wherein one or more of the first glass sheet, the second glass sheet, and the polymeric layer have a thickness that decreases from a center of curvature towards edges of the laminated glass pane.

12. The laminated glass pane of claim 10, wherein one or more of the first glass sheet, the second glass sheet, and the polymeric layer have a thickness that remains consistent the center of curvature towards edges of the laminated glass pane.

13. The laminated glass pane of claim 1, wherein the second glass sheet is a float glass sheet.

14. The laminated glass pane of claim 1, wherein the second glass sheet has a zebra angle of greater than or equal to 45 at a thickness of 0.7 mm.

15. The laminated glass pane of claim 14, wherein the zebra angle is greater than or equal to 55.

16. The laminated glass pane of claim 1, wherein the second glass sheet exhibits a ring-on-ring bending strength of more than 150 MPa and of less than 900 MPa.

17. The laminated glass pane of claim 16, wherein the ring-on-ring bending strength is more than 600 MPa.

18. The laminated glass pane of claim 1, wherein the second glass sheet comprises a combined toughened zone comprising: a potassium-exchanged surface layer with a thickness of less than 20 m as determined from a surface of the second glass sheet and a maximum compressive stress at the surface of more than 500 MPa; and a sodium-exchanged surface layer with a thickness of more than 40 m as determined from the surface, wherein the sodium-exchanged surface layer has a maximum local stress in an interior of a purely sodium-exchanged region that is less than 500 MPa.

19. The laminated glass pane of claim 1, wherein the first glass sheet comprises a soda-lime glass with a thickness between 1.5 mm and 2.5 mm or a lithium aluminum silicate glass with a thickness between at least 0.3 mm and at most 1.5 mm.

20. The laminated glass pane of claim 1, wherein the first glass sheet and/or the second glass sheet comprises a lithium aluminum silicate glass having: an Li.sub.2O content from 4.6 wt % to 5.4 wt %; an Na.sub.2O content from 8.1 wt % to 9.7 wt %; and an Al.sub.2O.sub.3 content from 16 wt % to 20 wt %.

21. The laminated glass pane of claim 1, wherein the second glass sheet is a chemically toughened glass sheet substantially due to an exchange of lithium ions by sodium ions.

22. A method for producing a laminated glass pane, comprising: providing a first glass sheet; providing a second glass sheet having a thickness between at least 0.3 mm and at most 1.5 mm and made of a lithium aluminum silicate glass; and bonding the first and second glass sheets to one another with a polymeric layer having a thickness between at least 0.5 mm and at most 1.7 mm to form the laminated glass pane, wherein the steps of providing the first and second glass sheets comprise providing glasses that, in a viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s, are matched so that temperatures at which the first and second glass sheets have a same viscosity only differ from each other by not more than 50 C.

23. The method of claim 22, further comprising curving the laminated glass pane.

24. The method of claim 23, wherein the curving step comprises curving the first and second glass sheets in a common process step or in successive process steps with common process parameters.

25. The method of claim 22, wherein the step of providing the first glass sheet and/or the second glass sheet comprises providing a chemically toughened first and/or second glass sheet, respectively.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIGS. 1 and 2 each show views of a laminated glass pane according to embodiments of the invention;

[0086] FIG. 3 shows the viscosity versus temperature profile for two different glasses;

[0087] FIGS. 4a and 4b show two schematic views of the imaging of stripe images when viewed through a glass sheet.

DETAILED DESCRIPTION

[0088] FIG. 1 is a schematic view, not drawn to scale, of a laminated glass pane 1 comprising a first glass sheet 2, a polymeric layer 3 disposed between and bonding the first glass sheet 2 to the second glass sheet 4, and finally the second glass sheet 4.

[0089] More generally, however, without being limited to the exemplary embodiment illustrated here, it is also possible for the laminated glass pane to comprise more than two glass sheets. For example, this may be the case when particularly high mechanical loads are expected and, accordingly, a particularly high strength of the laminated glass pane is desired.

[0090] The polymeric layer 3 has a thickness between at least 0.5 mm and at most 1.7 mm. It may be provided in the form of a film, for example a film comprising EVA and/or polyvinyl butyral, or in the form of a layer comprising a plurality of films, or a multilayer film. But it is also possible to form the polymeric layer in situ, by applying monomers to one of the two glass sheets 2, 4 and starting a polymerization reaction. Generally, it is also possible to form the polymeric layer 3 from laminated films. In particular, the films may also comprise PET and/or PE. In the case of a multilayer film, the layers may have different compositions and physical properties. Generally, the film or a layer of a multilayer film may have a low-E coating or a so-called solar control coating.

[0091] Furthermore, in the illustrated embodiment, the first glass sheet 2 has a greater thickness than the second glass sheet 4. This is advantageous, for example, if the first glass sheet has a lower intrinsic strength than the glass sheet 4, and so the thickness of the first glass sheet 2 is increased accordingly to ensure a sufficient strength of the laminated glass pane 1 as a whole.

[0092] The second glass sheet 4 has a thickness between at least 0.3 mm and at most 1.5 mm.

[0093] The glasses of the first and second glass sheets 2, 4 are matched to one another such that the temperatures at which the two glasses of the first and second glass sheets have the same viscosity in the viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s only differ from each other by not more than of 50 C., preferably by not more than 30 C., more preferably by not more than 20 C., and most preferably by not more than 10 C.

[0094] According to a further embodiment of the invention, the lithium aluminum silicate glass has a Young's modulus of at least 80 GPa, preferably at least 82 GPa, more preferably at least 84 GPa.

[0095] Preferably, the second glass sheet 4 is provided in the form of a chemically toughened glass sheet, preferably as a chemically toughened glass sheet with a compressive stress zone of at least 40 m thickness, the compressive stress being at least 150 MPa and at most 900 MPa.

[0096] According to a further embodiment of the invention, the compressive stress is at most 800 MPa, preferably at most 600 MPa. Such compressive stress is achieved in particular by toughening using a sodium nitrate-potassium nitrate mixture.

[0097] According to a further embodiment of the invention, the compressive stress is at most 500 MPa, preferably at most 400 MPa, more preferably at most 300 MPa, and most preferably at most 250 MPa. Such compressive stresses can be achieved in particular by toughening using a pure sodium nitrate melt.

[0098] Here, the nature of the respective toughening process can usually be identified based on a variation in the composition of the considered glass, i.e. of the glass sheet in question, for example, namely on the surface of the glass, i.e. the glass sheet, for example. If the toughening is accomplished by immersion into a sodium salt melt, such as a sodium nitrate melt, sodium will be enriched in the surface of the glass, whereas the surface layer will be depleted of lithium which has been exchanged by sodium. This depletion and enrichment can be revealed by ToF-SIMS surface profiles, for example.

[0099] If the toughening is performed in a salt melt which comprises a mixture of potassium and sodium salts, then the surface of the glass will in particular become enriched in potassium, which can also be detected by ToF-SIMS. Furthermore, a depletion in lithium will occur.

[0100] According to a further embodiment of the invention, the compressive stress zone has a depth of at least 50 rn, preferably of at least 60 rn, more preferably of at least 70 m, and most preferably of at least 80 m. Such a thickness of the compressive stress zone or ion exchange zone is preferably obtained by exchanging sodium for lithium.

[0101] According to a further embodiment of the invention, the second glass sheet 4 is configured such that the compressive stress zone has a depth of at least 40 rn thickness, preferably at least 50 m thickness, more preferably at least 60 m thickness, yet more preferably at least 70 m thickness, and most preferably at least 80 m thickness, and, preferably, the surfaces of the second glass sheet 4 are enriched in sodium and depleted of lithium in the region of the compressive stress zone (or ion exchange zone) compared to the bulk of glass sheet 4. Such a configuration of the glass sheet 4 can be achieved, for example, by an exchange in which the salt bath (the molten salt) comprises sodium nitrate and in particular solely consists of sodium nitrate, so that the compressive stress zone (or ion exchange zone) is obtained by replacing lithium by sodium.

[0102] According to one embodiment of the invention, the laminated glass pane 1 is provided in the form of a curved laminated glass pane such that the outwardly facing side of the second glass sheet 2 is curved concavely.

[0103] Preferably, the second glass sheet 4 is formed in a melting process followed by a hot forming process. The hot forming process comprises, for example, a drawing process, such as an up-draw process, a down-draw process, or an overflow fusion process, or a float process. It has been found that the aforementioned processes allow to obtain particularly smooth and even surfaces of the glass sheets produced in this way. This, in turn, is advantageous for a correspondingly good view through the laminated glass pane 1 and also for good mechanical strength values both for the laminated glass pane 1 and for the glass sheet produced in this way, here the glass sheet 4, by way of example. Particularly preferably, the second glass sheet 4 is a float glass.

[0104] According to a further embodiment of the invention, the second glass sheet 4 has a zebra angle greater than or equal to 45, in particular greater than or equal to 50, more preferably greater than or equal to 55, at a thickness of 0.7 mm.

[0105] According to a further embodiment of the invention, the second glass sheet 4 has a ring-on-ring bending strength of more than 150 MPa, in particular more than 250 MPa, preferably more than 300 MPa, yet more preferably more than 400 MPa, yet more preferably more than 500 MPa, and most preferably more than 600 MPa, and of less than 900 MPa.

[0106] In a particularly preferred embodiment of the laminated glass pane 1, the second glass sheet 4 has a combined toughened zone which comprises a potassium-exchanged surface layer with a thickness of less than 20 m as determined from the glass surface, with a maximum compressive stress at the surface of more than 500 MPa, preferably more than 600 MPa; and a sodium-exchanged surface layer with a thickness of more than 40 m, preferably more than 50 m, more preferably more than 60 m, yet more preferably more than 70 m, and most preferably more than 80 m as determined from the glass surface, wherein the maximum local stress in the interior of the purely sodium-exchanged surface layer is less than 500 MPa, preferably less than 400 MPa.

[0107] The maximum stress in the potassium-exchanged surface layer is at most 900 MPa. The maximum stress in the sodium-exchanged surface layer may be at least 50 MPa.

[0108] This means that in the surface layer of the second glass sheet 4, i.e. to a thickness of less than 20 m (so-called potassium exchange zone), potassium ions have been exchanged for sodium ions and for lithium ions to a lesser extent. Furthermore, the glass sheet 4 has a sodium-exchanged surface layer (so-called sodium exchange zone), which may at least partially overlap with the potassium-exchanged surface in terms of its extent in the glass. This sodium-exchanged surface layer has a thickness of more than 40 m, in particular more than 50 m, preferably more than 60 m, more preferably more than 70 m, and most preferably more than 80 m. Here, the alkali ions such as lithium ions have been replaced by sodium ions, at least partially.

[0109] According to a further embodiment of the invention, the first glass sheet 2 comprises a soda-lime glass with a thickness between 1.5 mm and 2.5 mm or a lithium aluminum silicate glass with a thickness between at least 0.3 mm and at most 1.5 mm. By way of example, and without being limited to the exemplary embodiment illustrated in FIG. 1, it is therefore also possible for the first and second glass sheets 2, 4 to have the same thickness.

[0110] According to a preferred embodiment of the invention, the second glass sheet comprises a lithium aluminum silicate glass having a Li.sub.2O content from 4.6 wt % to 5.4 wt % and an Na.sub.2O content from 8.1 wt %. to 9.7 wt % and an Al.sub.2O.sub.3 content from 16 wt % to 20 wt %.

[0111] According to yet another embodiment of the invention, the second glass sheet 4 comprises the following constituents:

TABLE-US-00005 58 to 65 wt % SiO.sub.2 16 to 20 wt % Al.sub.2O.sub.3 0.1 to 1 wt % B.sub.2O.sub.3 4.6 to 5.4 wt % Li.sub.2O 8.1 to 9.7 wt % Na.sub.2O optionally 0.05 to 1.0 wt % K.sub.2O 0.2 to 2.0 wt % CaO 2.5 to 5.0 wt % ZrO.sub.2.

[0112] Optionally, one or more of the constituents SnO.sub.2, CeO.sub.2, P.sub.2O.sub.5, and ZnO may be included, with a content of 0 wt % to 2.5 wt % in total.

[0113] Preferably, in this case, the second glass sheet 4 comprises the following constituents:

TABLE-US-00006 60 to 62 wt % SiO.sub.2 17.5 to 19.5 wt % Al.sub.2O.sub.3 0.5 to 0.7 wt % B.sub.2O.sub.3 4.8 to 5.2 wt % Li.sub.2O 8.5 to 9.5 wt % Na.sub.2O 0.2 to 0.5 wt % K.sub.2O 0.5 to 1.2 wt % CaO 3.2 to 3.8 wt % ZrO.sub.2.

[0114] Optionally, one or more of the constituents SnO.sub.2, CeO.sub.2, P.sub.2O.sub.5, and ZnO may be included, with a content of 0.25 wt % to 1.6 wt % in total.

[0115] Furthermore preferably, the second glass sheet 4 comprises the following constituents:

TABLE-US-00007 61 to 62 wt % SiO.sub.2 17.5 to 18.5 wt % Al.sub.2O.sub.3 0.5 to 0.7 wt % B.sub.2O.sub.3 4.9 to 5.1 wt % Li.sub.2O 8.8 to 9.3 wt % Na.sub.2O 0.2 to 0.5 wt % K.sub.2O 0.5 to 1.2 wt % CaO 3.2 to 3.8 wt % ZrO.sub.2.

[0116] Optionally, one or more of the constituents SnO.sub.2, CeO.sub.2, P.sub.2O.sub.5, and ZnO may be included, with a content of 0.5 wt % to 1.0 wt % in total.

[0117] According to a further preferred embodiment of the invention, the second glass sheet 4 comprises the following composition, in mol %:

TABLE-US-00008 60 to 70 SiO.sub.2 10 to 13 Al.sub.2O.sub.3 0.0 to 0.9 B.sub.2O.sub.3 9.6 to 11.6 Li.sub.2O 8.2 to less than 10 Na.sub.2O 0.0 to 0.7 K.sub.2O 0.0 to 0.2 MgO 0.2 to 2.3 CaO 0.0 to 0.4 ZnO 1.3 to 2.6 ZrO.sub.2 0.0 to 0.5 P.sub.2O.sub.5 0.003 to 0.100 Fe.sub.2O.sub.3 0.0 to 0.3 SnO.sub.2 0.004 to 0.200 CeO.sub.2.

[0118] Preferably, the following relationships apply for the composition of the lithium aluminum silicate glass:

(Li.sub.2O+Al.sub.2O.sub.3)/(Na.sub.2O+K.sub.2O)>2

0.47<Li.sub.2O/(Li.sub.2O+Na.sub.2O+K.sub.2O)<0.7

0.8<CaO+Fe.sub.2O.sub.3+ZnO+P.sub.2O.sub.5+B.sub.2O.sub.3+CeO.sub.2<3,

[0119] wherein at least four of the six oxides are included in the glass composition.

[0120] Furthermore preferably, the lithium aluminum silicate glass has a glass transition temperature T.sub.g of less than 540 C. and/or a processing temperature of less than 1150 C.

[0121] Furthermore, according to another embodiment, the laminated glass pane 1 is configured such that the second glass sheet 4, at a thickness of 0.7 mm, exhibits a transmittance of more than 91.5% at a wavelength of 840 nm, of more than 91.5% at a wavelength of 560 nm, and of more than 90% at 380 nm. As already mentioned above, this is particularly advantageous for achieving of a good view through the pane 1, so that passenger safety is further improved in this way.

[0122] Preferably, the laminated glass pane 1 is designed such that the temperatures at which the glasses of the first glass sheet 2 and of the second glass sheet 4 have the same viscosity in the viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s only differ from each other by a maximum of 50 C., preferably by a maximum of 30 C., more preferably by a maximum of 20 C., and most preferably by a maximum of 10 C. at a respective identical viscosity.

[0123] According to yet another embodiment of the invention, the second glass sheet 4 is provided in a chemically toughened form, substantially by an exchange of lithium ions by sodium ions. A glass sheet is referred to as being toughened substantially by an exchange of lithium ions by sodium ions, if the substantial portion of preliminary stress, i.e. at least 80% of the generated preliminary stress, is caused by the exchange of lithium ions by sodium ions. A glass sheet is in particular toughened substantially by an exchange of lithium ions by sodium ions if the preliminary stress is exclusively achieved by this exchange.

[0124] Another aspect of the present invention relates to a method for producing a laminated glass pane 1. In this case, a first glass sheet 2 and a second glass sheet 4 are provided. The second glass sheet has a thickness between at least 0.3 mm and at most 1.5 mm and comprises a lithium aluminum silicate glass. The first glass sheet 2 and the second glass sheet 4 are bound to one another by a polymeric layer 3 with a thickness between at least 0.5 mm and at most 1.7 mm. The glasses of the first glass sheet 2 and of the second glass sheet 4 are matched such that the temperature at which the glasses of the first glass sheet 2 and of the second glass sheet 4 have the same viscosity in the viscosity range between 10.sup.7 dPa.Math.s and 10.sup.10 dPa.Math.s only differ from each other by a maximum of 50 C., preferably by a maximum of 30 C., more preferably by a maximum of 20 C., and most preferably by a maximum of 10 C.

[0125] According to a further embodiment of the method, the laminated glass pane 1 is curved, for example uniaxially curved or biaxially curved. In the context of the present invention, a glass sheet is referred to as being uniaxially curved when the glass sheet is curved in only one direction. A glass sheet is referred to as being biaxially curved when the glass sheet is curved in two directions, for example in the form of a shell or a dome-like shape.

[0126] According to a preferred embodiment of the method, the first glass sheet 1 and the second glass sheet 4 are bent in the same process step or in succession using the same process parameters.

[0127] FIG. 2 shows a further embodiment of a laminated glass pane 1. Here, again, the laminated glass pane 1 comprises a first glass sheet 2, a polymeric layer 3, and a second glass sheet 4. However, this time the laminated glass pane 1 has a curved shape. It is possible in this case, that the thickness of the individual glass sheets 2, 4 and of the polymeric layer 3 decreases from the center of the laminated glass pane 1 towards the edges thereof, as illustrated. However, it is also possible that the thickness of the individual glass sheets 2, 4 and also that of the polymeric layer 3 is consistent, or that only individual ones of the layers 2, 3, 4 constituting the laminated glass pane 1 have a thickness that varies over the cross section of the pane 1. For example, one or more of the layers may be wedge-shaped.

[0128] In the present case, the laminated glass pane 1 is formed such that the outwardly facing surface 41 of the second glass sheet 4 is curved concavely.

[0129] More generally, without being limited to the example illustrated here, the laminated glass pane 1 may also be designed such that the outwardly facing surface 21 of the first glass sheet 2 is curved concavely.

[0130] FIG. 3 shows the viscosity curve for two different glasses 5 and 6. The y-axis represents the decadic logarithm of the viscosity, in dPa.Math.s, and the x-axis represents the temperature, in C. In the viscosity range between 10.sup.7 and 10.sup.10 dPa.Math.s, which is of particular relevance for producing a laminated glass pane according to embodiments of the invention, the viscosity curves of the two glasses 5 and 6 are very close to one another. In the case of the glasses selected here by way of example, glass 5 is a so-called soda-lime glass, glass 6 is a lithium aluminum silicate glass.

[0131] FIG. 4a is a schematic view of a so-called zebra board when viewed through the glass sheet 4 (not shown here), and in this case the angle between the glass sheet 4 and the zebra board is 0, i.e. the glass sheet and the board are arranged parallel to each other and the viewing direction is perpendicular through the glass sheet.

[0132] More generally, without being limited to the view of such a striped board illustrated here, different embodiments of such a zebra board are possible. For example, the stripes may extend in parallel to the diagonal of the zebra board, as exemplified herein. However, other embodiments are also possible. In particular boards are available in which the stripes define an angle of 30 with one of the edges bounding the board, for example.

[0133] In such an arrangement in which the glass sheet 4 and the stripe board or zebra board are arranged parallel to each other, as is the case in FIG. 4a, the image will usually not be distorted at all.

[0134] The situation is different when an angle is created between the glass sheet 4 and the board. Depending on the quality of the glass sheet, i.e. in particular depending on how strongly thickness variations are pronounced in the glass sheet, this effect will appear stronger or weaker. Therefore, a measure of the quality of the glass sheet is the maximum angle at which no distortion is perceived any more. FIG. 4b illustrates a distortion of the stripe image, by way of example.

LIST OF REFERENCE NUMERALS

[0135] 1 Laminated glass [0136] 2 First glass sheet [0137] 21 Outwardly facing surface of glass sheet 2 [0138] 3 Polymeric layer [0139] 4 Second glass sheet [0140] 41 Outwardly facing surface of glass sheet 4