Laminated glazing

Abstract

A curved laminated glazing includes an outer sheet of a soda-lime-silica colored glass and an inner sheet of a chemically-toughened sodium aluminosilicate clear glass having a thickness e2 ranging from 0.4 to 1.1 mm, the outer and inner sheets being joined together by a lamination interlayer, the colored glass having a chemical composition comprising a weight content of total iron, expressed in the form Fe.sub.2O.sub.3, ranging from 0.6 to 2.2%, the glasses of the inner and outer sheets being selected so that 0≤T10.sub.in−T10.sub.out≤20° C., where T10.sub.in is the temperature T10 of the glass of the inner sheet and T10.sub.out is the temperature T10 of the glass of the outer sheet, the temperature T10 being the temperature at which the glass considered has a viscosity of 10.sup.10 dPa.Math.s.

Claims

1. A curved laminated glazing comprising an outer sheet of a soda-lime-silica colored glass and an inner sheet of a chemically-toughened sodium aluminosilicate clear glass having a thickness e2 ranging from 0.4 to 1.1 mm, said outer and inner sheets being joined together by means of a lamination interlayer, said colored glass having a chemical composition comprising a weight content of total iron, expressed in the form Fe.sub.2O.sub.3, ranging from 0.6 to 2.2%, and the glasses of the inner and outer sheets being selected so that 0≤T10.sub.in−T10.sub.out≤20° C., where T10.sub.in is the temperature T10 of the glass of the inner sheet and T10.sub.out is the temperature T10 of the glass of the outer sheet, the temperature T10 being the temperature at which the glass considered has a viscosity of 10.sup.10 dPa.s.

2. The laminated glazing as claimed in claim 1, wherein a thickness e1 of the outer sheet is within a range of from 1.6 to 2.4 mm.

3. The laminated glazing as claimed in claim 2, wherein the ratio R=e2/e1.sup.2 is at most 0.40.

4. The laminated glazing as claimed in claim 1, wherein the temperature T10.sub.out is within a range of from 655 to 675° C.

5. The laminated glazing as claimed in claim 1, wherein the temperature T10.sub.in is within a range of from 660 to 680° C.

6. The laminated glazing as claimed in claim 1, wherein T10.sub.in−T10.sub.out≥5° C.

7. The laminated glazing as claimed in claim 1, wherein the colored glass has a chemical composition comprising the following constituents, in a weight content that varies within the limits defined below: TABLE-US-00005 SiO.sub.2 68-75% Al.sub.2O.sub.3  0-3% CaO + MgO 11-16.2%.sup.  MgO  0-6.5% Na.sub.2O 9-12.4%  K.sub.2O  0-1.5%.

8. The laminated glazing as claimed in claim 1, wherein the weight content of total iron of the colored glass, expressed in the form Fe.sub.2O.sub.3, is within a range of from 0.7 to 1.8%.

9. The laminated glazing as claimed in claim 1, wherein the colored glass has a redox ratio, defined as the ratio between the weight content of ferrous iron, expressed in the form FeO, and the weight content of total iron, expressed in the form Fe.sub.2O.sub.3, ranging from 0.22 to 0.31.

10. The laminated glazing as claimed in claim 1, wherein the outer sheet is made of glass that is not mechanically reinforced.

11. The laminated glazing as claimed in claim 1, wherein a thickness of the laminated glazing is at most 5 mm.

12. The laminated glazing as claimed in claim 1, which is doubly curved and has a double-bending depth of at least 20 mm.

13. A glazing for a transport vehicle, comprising a laminated glazing as claimed in claim 1.

14. A process for obtaining a curved laminated glazing as claimed in claim 1, comprising: a bending step, wherein a sheet of a sodium aluminosilicate clear glass having a thickness e2 ranging from 0.4 to 1.1 mm, referred to as inner glass sheet and intended to become the inner sheet of the glazing, and a sheet of a soda-lime-silica colored glass having a chemical composition comprising a weight content of total iron, expressed in the form Fe.sub.2O.sub.3, ranging from 0.6 to 2.2%, referred to as outer glass sheet and intended to become the outer sheet of the glazing, are bent together, said inner glass sheet being positioned above said outer glass sheet, the two glass sheets being separated by means of an interlayer powder, then a chemical toughening step, wherein the inner glass sheet is bought into contact with a molten potassium salt, then a lamination step, wherein the inner and outer glass sheets are joined together by means of a lamination interlayer.

15. The laminated glazing as claimed in claim 1, wherein the thickness e2 is from 0.4 to 0.7 mm.

16. The laminated glazing as claimed in claim 3, wherein the ratio R=e2/e1.sup.2 is at most 0.30.

17. The laminated glazing as claimed in claim 8, wherein the weight content of total iron of the colored glass, expressed in the form Fe.sub.2O.sub.3, is within a range of from 0.8 to 1.5%.

18. The laminated glazing as claimed in claim 9, wherein the weight content of total iron, expressed in the form Fe.sub.2O.sub.3, ranging from 0.24 to 0.29.

19. The laminated glazing as claimed in claim 11, wherein the thickness of the laminated glazing is at most 4 mm.

20. The glazing for a transport vehicle as claimed in claim 13, wherein the transport vehicle is a motor vehicle and the glazing is a windshield or a roof.

Description

(1) According to a first preferred embodiment, the weight content of MgO is at most 1%, in particular 0.5% and even 0.1%. The content of CaO is advantageously at least 11.5%, or else 12%. The content of Na.sub.2O is preferably at least 10%, or else 11%. It is advantageously at most 12%. Particularly preferred compositions comprise the following constituents, in a weight content that varies within the limits defined below:

(2) TABLE-US-00002 SiO.sub.2 71-74.2% Al.sub.2O.sub.3    0-3% CaO 11.5-13% MgO    0-1% Na.sub.2O 11-12.4%, in particular 11-12%, K.sub.2O   0-1.5%.

(3) According to a second preferred embodiment, the weight content of MgO is at least 4%, or else 4.5% or 5% and/or at least 6%. The content of CaO is preferably between 9 and 11%, in particular between 9 and 10.5%. The content of Na.sub.2O is advantageously at least 9.5%, or else 10% and/or at most 12% or 11%. Particularly preferred compositions comprise the following constituents, in a weight content that varies within the limits defined below:

(4) TABLE-US-00003 SiO.sub.2 70-74% Al.sub.2O.sub.3  0-2% CaO 9-10.5%  MgO 4-6.5%, in particular 4-6% Na.sub.2O 10-11% K.sub.2O   0-1%.

(5) According to a third embodiment, the weight content of CaO is at least 9%, in particular 10% and/or at most 12%, in particular 11%. The weight content of MgO is preferably at least 4% and/or at most 5%. The content of Na.sub.2O is preferably at least 11%.

(6) Particularly preferred compositions comprise the following constituents, in a weight content that varies within the limits defined below:

(7) TABLE-US-00004 SiO.sub.2 69-72%, in particular 69-71% Al.sub.2O.sub.3 1-3%, in particular 1.7-3% CaO 10-12%, in particular 10.1-11% MgO 4-5% Na.sub.2O 11-12.4%, in particular 11.5-12% K.sub.2O 0-1%, in particular 0-0.3%.

(8) The weight content of total iron of the colored glass, expressed in the form Fe.sub.2O.sub.3, is preferably at least 0.7%, in particular 0.8%. It is preferably at most 1.9%, in particular 1.6%, or else 1.4%. It is preferably within a range of from 0.7 to 1.8%, in particular from 0.8 to 1.5%.

(9) The redox ratio of the colored glass is preferably at least 0.22, in particular 0.25. It is preferably at most 0.31, in particular 0.30, or else 0.29 or 0.28. The redox ratio is preferably within a range of from 0.22 to 0.31, in particular from 0.24 to 0.29, or else from 0.25 to 0.27. The redox ratio corresponds to the ratio between the weight content of ferrous iron, expressed in the form FeO, and the weight content of total iron, expressed in the form Fe.sub.2O.sub.3.

(10) This choice of weight contents of total iron and/or of redox ratio makes it possible to obtain glazings having good optical and thermal properties, in particular in terms of light transmission and direct solar transmission.

(11) The colored glass preferably contains no colorants other than iron oxide or titanium oxide. The latter is an impurity frequently contained in certain raw materials and may contribute to lightly coloring the glass. The content of titanium oxide is generally at most 0.1%, or else 0.06%. The colored glass preferably does not contain cobalt oxide, nickel oxide, chromium oxide, selenium, copper oxide, vanadium oxide, manganese oxide. It preferably contains no rare-earth element oxide, in particular no cerium oxide. According to one variant, the colored glass may contain very small amounts of at least one aforementioned colorant in order to adjust the optical properties. In this case, the total content of colorants other than the iron and titanium oxides is preferably at most 40 ppm (1 ppm=0.0001%), in particular 30 or 20 ppm.

(12) In order to improve the resistance to gravel impact, the outer sheet is preferably made of glass that is not mechanically reinforced. Therefore, in this case, it is neither toughened nor hardened. The expression “not mechanically reinforced” is understood to mean that the glass sheet has not been subjected to reinforcement by chemical toughening or using forced cooling means for the purpose of creating high compressive stresses at the surface of the glass sheet. This definition does not however exclude the possibility of using cooling means that are conventionally used and necessary for respecting the cycle times or for obtaining form stresses. During a process for forming motor vehicle glazings, it is in fact necessary to cool the glass after the forming thereof in order to respect the cycle times and to create form stresses by placing the periphery of the glazing under compression in order to increase the resistance of the edges to breaking. The expression “not mechanically reinforced” does not therefore exclude the presence of edge stresses.

(13) The glass that is not mechanically reinforced is preferably such that the residual core tensile stress is at most 12 MPa, in particular 5 MPa, or else 2 MPa. Such stress values are in particular obtained with cooling rates of at most 1° C. per second after bending, more specifically between the outlet of the bending furnace and the zone in which the temperature of the glass corresponds to its annealing temperature. The measurement of the residual stress is in particular carried out on a test specimen obtained by cutting from the glazing a parallelepipedal test specimen of 10 mm×50 mm, by separating the first glass sheet from the lamination interlayer, for example by thermally treating the test specimen at a temperature of from 150 to 200° C., then by measuring the stresses in the thickness of the glass sheet. The measurement of the stresses may for example be carried out using a biasographe, described in chapter 8 of the book “Photoelasticity of Glass” by H. Aben, C. Guillemet (1993) Springer Verlag.

(14) The glazing is curved. In order to achieve this, the two glass sheets are bent, generally together, before being assembled by means of the lamination interlayer. The bending may be carried out in a known manner, for example by gravity bending (the glass deforming under its own weight) or by press bending, at temperatures typically ranging from 600 to 680° C. During the bending, the inner glass sheet is placed above the outer glass sheet. As indicated previously, to prevent the glass sheets from sticking to one another during the bending, the glass sheets are preferably kept at a distance by positioning between them an interlayer powder that ensures a space of several tens of micrometers, typically from 20 to 50 μm. The interlayer powder is for example based on calcium carbonate and/or magnesium carbonate.

(15) The lamination may be carried out in a known manner by an autoclave treatment, for example at temperatures of from 110 to 160° C. and under a pressure ranging from 10 to 15 bar. Prior to the autoclave treatment, the air trapped between the glass sheets and the lamination interlayer may be eliminated by calendering or by vacuum.

(16) The direct solar transmission of the glazing is preferably at most 52%, in particular 50%, and even 48% or 46%, or else 45%. It is in general at least 35%. The direct solar transmission is determined according to the standard ISO 9050:2003.

(17) The light transmission of the glazing is preferably at least 70%, in particular 71%. It is advantageously at most 80%, in particular at most 78% or 77% and even 75% or 74%. The light transmission is calculated from an experimental spectrum produced on the glazing considered, by taking into account the illuminant A defined by the standard ISO 11664-2 and the CIE 1931 reference observer) (2°) defined by the standard ISO 11664-1.

(18) The thickness of the glazing is preferably at most 5 mm, in particular 4.5 mm, or else 4 mm. It is in general at least 2.8 mm, in particular 3 mm.

(19) As indicated above, the invention makes it possible to prevent the appearance of edge corrugations following the bending, which is particularly difficult to obtain in the case of complex, large-sized and/or highly curved glazings.

(20) The glazing preferably has a surface area of at least 1.5 m.sup.2, or else 1.6 or 1.8 m.sup.2.

(21) The glazing is preferably doubly curved. It preferably has a double-bending depth (often simply referred to as “double-bending”) of at least 20 mm. A glazing is doubly curved if it cannot be included in a surface generated by straight lines perpendicular to one and to the same plane. In practice, in the motor vehicle field, a glazing is said to be doubly curved when the cross sections of the glazing, in the plane of symmetry of the glazing and in a plane orthogonal to said plane of symmetry, exhibit a curvature. The double-bending is then defined as being the minimum of the largest bow in the planes parallel to the plane of symmetry of the glazing and of the largest bow in the planes orthogonal to said plane of symmetry. When there is no obvious symmetry, instead of the plane of symmetry, as reference, in the usage position of the glazing in the vehicle, the vertical plane parallel to the displacement (in a straight line) of the vehicle is taken for the glazings that are not side windows (windshields, roofs) and the vertical plane perpendicular to the displacement (in a straight line) of the vehicle is taken for the side windows. A last equivalent possibility is to take the vertical plane parallel to the displacement of the glazing in the bending furnace when this furnace is horizontal.

(22) At least one glass sheet may be coated on a face turned toward the lamination interlayer with a stack of electrically-conductive and/or low-emissivity thin layers, in order to obtain a heated glazing or to further improve the thermal insulation of the glazing. Such a stack preferably comprises at least one thin silver layer flanked by at least two thin dielectric layers.

(23) The lamination interlayer preferably comprises at least one sheet of polyvinyl acetal, in particular of polyvinyl butyral (PVB).

(24) The lamination interlayer may be colored or colorless in order, if necessary, to adjust the optical or thermal properties of the glazing.

(25) The lamination interlayer may advantageously have sound absorption properties in order to absorb airborne or solidborne sounds. It may in particular consist, for this purpose, of three polymeric sheets, including two so-called outer sheets of PVB flanking an inner polymeric sheet, optionally made of PVB, of lower hardness than that of the outer sheets.

(26) The lamination interlayer may also have thermal insulation properties, in particular properties of reflection of the infrared radiation. It may, for this purpose, comprise a coating of thin layers with low emissivity, for example a coating comprising a thin silver layer or a coating alternating dielectric layers of different refractive indices, which is deposited on an inner PET sheet flanked by two outer PVB sheets.

(27) The thickness of the lamination interlayer is generally within a range of from 0.3 to 1.5 mm, in particular from 0.5 to 1 mm. The lamination interlayer may have a thinner thickness on an edge of the glazing than at the center of the glazing in order to prevent the formation of a ghost image in the event of using a head-up display (HUD) system.

(28) The following examples illustrate the invention in a nonlimiting manner.

(29) Laminated curved glazings were manufactured as described in detail below. The inner and outer glass sheets were cut then positioned on one another, more specifically the inner sheet on top of the outer sheet, the two sheets being separated by an interlayer powder made of magnesium carbonate, making a space of around 20 μm between the two sheets. The two glass sheets, positioned on a bending skeleton, were then placed in a bending furnace in order to obtain the desired curvature. The bending cycle used is a conventional cycle for the production of windshields: a temperature increase for 380 s to reach a hold during which the glass sheets remain for 30 s at a maximum bending temperature indicated below, then cooling at a rate of 0.80° C./s. After cooling and washing, the inner glass sheet was chemically toughened by submerging the glass sheet in a molten potassium nitrate salt so as to obtain an upper surface stress of 550 MPa and a thickness in compression of 40 μm. The two glass sheets were then laminated in a known manner using a 0.76-mm thick PVB lamination interlayer.

(30) The inner sheet is made of a sodium aluminosilicate clear glass. Its thickness is 0.5 mm. The T10.sub.in temperature of this glass (before chemical toughening) is equal to 665° C.

(31) The outer sheet is made of a soda-lime-silica colored glass that is not mechanically reinforced. Its thickness is 1.6 mm. The content of total iron, expressed as Fe.sub.2O.sub.3, is 1%, with a redox ratio of 0.26.

(32) In a comparative example, the chemical composition by weight of the soda-lime-silica glass was the following: SiO.sub.2: 72.4%; Al.sub.2O.sub.3: 0.6%; Fe.sub.2O.sub.3: 1.0%; Na.sub.2O: 13.4%; K.sub.2O: 0.1%, CaO: 9.0%; MgO: 3.1%. The T10.sub.out temperature of this glass is equal to 635° C., so that ΔT10 is equal to 30° C. The maximum bending temperature was 635° C.

(33) In an example according to the invention, the chemical composition by weight of the soda-lime-silica glass was the following: SiO.sub.2: 69.3%; Al.sub.2O.sub.3: 2.0%; Fe.sub.2O.sub.3: 1.0%; Na.sub.2O: 11.9%; K.sub.2O: 0.7%, CaO: 10.5%; MgO: 4.3%. The T10.sub.out temperature of this glass is equal to 660° C., so that ΔT10 is equal to 5° C. The maximum bending temperature was 655° C.

(34) In the case of the comparative example, edge corrugations are visible to the naked eye. These corrugations of the inner glass sheet appear as a periodic local detachment between the two glass sheets. At the edges, the inner sheet is, in places, detached from the outer sheet by a distance of 20 mm. On the other hand, in the case of the example according to the invention, no corrugation is observed.