Laminated glazing

Abstract

A laminated glazing comprising first and second sheets of glass joined together by an interlayer structure comprising at least a first layer of adhesive interlayer material is disclosed. The surface compressive stress in a central region of a first major surface of the first sheet of glass is dependent upon the thickness of the first sheet of glass. For a thickness t of the first sheet of glass between 1.4 mm and 2.6 mm the minimum surface compressive stress CSmin (in MPa) in the central region of the first major surface of the first sheet of glass is given by CSmin(MPa)=21.0×t3−118.6×t2+236.9×t−a1, wherein a1 is between 135 MPa and 140 MPa. The second sheet of glass may be a sheet of chemically strengthened glass having a thickness between 0.3 mm and 1.0 mm. The laminated glazing may be fixed or movable in an aperture in a vehicle.

1 . A laminated glazing comprising
 a first sheet of glass joined to a second sheet of glass by an interlayer structure comprising at least a first layer of adhesive interlayer material,   wherein the first and second sheets of glass each have respectively a first major surface and a second opposing major surface and the laminated glazing is arranged such that at least a portion of the second major surface of the first sheet of glass faces the first major surface of the second sheet of glass;   wherein the first sheet of glass has a surface compressive stress in at least a central region of the first major surface of the first sheet of glass of at least CS min  and wherein for a thickness t of the first sheet of glass between 1.4 mm and 2.6 mm, CS min  in MPa is given by
     CS   min (MPa)=21.0× t   3 −118.6× t   2 +236.9× t−a   1  
 
   wherein a 1  is between 135 MPa and 140 MPa.   
     
     
         2 . A laminated glazing according to  claim 1 , wherein the surface compressive stress in the central region of the first major surface of the first sheet of glass is less than CS max , wherein CS max  in MPa is given by
     CS   max (MPa)=28.3× t   3 −139.8× t   2 +244.6× t−b   1  
   wherein b 1  is between 120 MPa and 126 MPa.   
     
     
         3 . A laminated glazing according to  claim 1 , wherein the thickness of the second sheet of glass is greater than 0.3 mm and/or wherein the thickness of the second sheet of glass is less than 1.0 mm. 
     
     
         4 . A laminated glazing according to  claim 1 , wherein the second sheet of glass has been chemically strengthened; and/or wherein the second sheet of glass has been chemically strengthened to have surface compressive stress greater than 400 MPa; and/or wherein the second sheet of glass is chemically strengthened to have a depth of layer (DOL) between 10 μm and 60 μm. 
     
     
         5 . A laminated glazing comprising
 a first sheet of glass joined to a second sheet of glass by an interlayer structure comprising at least a first layer of adhesive interlayer material,   wherein the first and second sheets of glass each have respectively a first major surface and a second opposing major surface and the laminated glazing is arranged such that at least a portion of the second major surface of the first sheet of glass faces the first major surface of the second sheet of glass;   the first sheet of glass having a thickness greater than 2.6 mm and less than 8 mm, and wherein a surface compressive stress in a central region of the first major surface of the first sheet of glass is between 50 MPa and 150 MPa;   the second sheet of glass being a sheet of chemically strengthened glass having a thickness between 0.3 mm and 1.0 mm.   
     
     
         6 . A laminated glazing according to  claim 5 , wherein the second sheet of glass is an alkali aluminosilicate glass composition and/or wherein the second sheet of glass includes at least about 6 wt % aluminium oxide. 
     
     
         7 . A laminated glazing according to  claim 5 , wherein: i) the second sheet of glass has a composition comprising 66-72 mol. % SiO 2 , 1-4 mol. % Al 2 O 3 , 8-15 mol. % MgO, 1-8 mol. % CaO, 12-16 mol. % Na 2 O; or ii) the second sheet of glass has a composition comprising (by weight) 58% to 70% SiO 2 , 5% to 15% Al 2 O 3 , 12% to 18% Na 2 O, 0.1% to 5% K 2 O, 4% to 10% MgO and 0% to 1% CaO with the provisos that the sum of the Al 2 O 3  and MgO exceeds 13%, that the sum of the amounts of Al 2 O 3  plus MgO divided by the amount of K 2 O exceeds 3 and that the sum of the Na 2 O plus K 2 O plus MgO exceeds 22%. 
     
     
         8 . A laminated glazing according to  claim 5 , wherein the second sheet of glass is chemically strengthened to have surface compressive stress greater than 400 MPa. 
     
     
         9 . A laminated glazing according to  claim 5 , wherein the second sheet of glass is chemically strengthened to have a depth of layer (DOL) between 10 μm and 60 μm. 
     
     
         10 . A laminated glazing according to  claim 5 , wherein the first sheet of glass has a glass composition comprising (by weight), SiO 2  69-74%; Al 2 O 3  0-3%; Na 2 O 10-16%; K 2 O 0-5%; MgO 0-6%; CaO 5-14%; SO3 0-2% and Fe 2 O 3  0.005-2%. 
     
     
         11 . A laminated glazing according to  claim 5 , wherein the first layer of adhesive interlayer material is coextensive with the first and/or second sheet of glass. 
     
     
         12 . A laminated glazing according to  claim 5 , wherein the first layer of adhesive interlayer material comprises polyvinyl butyral (PVB), acoustic modified PVB, a copolymer of ethylene such as ethylene vinyl acetate (EVA), polyurethane (PU), polycarbonate, poly vinyl chloride (PVC) or a copolymer of ethylene and methacrylic acid and/or wherein the first layer of adhesive interlayer material has a thickness between 0.3 mm and 2.3 mm. 
     
     
         13 . A laminated glazing according to  claim 5  having a solar control function. 
     
     
         14 . A laminated glazing according to  claim 13 , wherein the solar control function is provided by a solar control coating on the first and/or second sheet of glass, and/or wherein the solar control function is provided by the first and/or second sheet of glass. 
     
     
         15 . A laminated glazing according to  claim 13 , wherein the solar control function is provided by the first layer of adhesive interlayer material. 
     
     
         16 . A laminated glazing according to  claim 13 , wherein the interlayer structure comprises a second layer of adhesive interlayer material and an intermediate sheet, the intermediate sheet being between the first and second layers of adhesive interlayer material, and wherein the solar control function is provided by the intermediate sheet. 
     
     
         17 . A laminated glazing according to  claim 16 , wherein the intermediate sheet is a carrier sheet that carries an infrared reflecting coating and/or wherein the first and/or second layer of adhesive interlayer material comprises functional inclusions that reduce the amount of solar radiation that may otherwise be transmitted through the laminated glazing. 
     
     
         18 . A laminated glazing according to  claim 5 , wherein the first and second sheets of glass each have a respective periphery and the periphery of the second sheet of glass is contiguous with the periphery of the first sheet of glass or wherein the periphery of the second sheet of glass is enclosed within the periphery of the first sheet of glass. 
     
     
         19 . A laminated glazing according to  claim 5 , wherein the first and/or second sheet of glass comprises a respective first connection portion for connecting the laminated glazing to a mechanism for moving the laminated glazing. 
     
     
         20 . A vehicle having an aperture, wherein a laminated glazing according to  claim 1  is (i) fixed within the aperture or (ii) is movable within the aperture or (iii) is movable within the aperture by a mechanism connected to the first connection portion of the first or second sheet of glass.