Laminated glazing

Abstract

A laminated glazing for a vehicle windscreen is described comprising a first sheet of glass joined to a second sheet of glass by an interlayer structure comprising at least one sheet of adhesive interlayer material. The first sheet of glass has a first major surface and an opposing second major surface and the second sheet of glass has a third major surface and an opposing fourth major surface. The laminated glazing is arranged such that the second major surface faces the third major surface. The laminated glazing has at least a first marked surface being the first major surface, the second major surface, the third major surface or the fourth major surface. The first marked surface has at least a first mark thereon, and the first mark comprises at least a first protuberant portion. A method of making such a laminated glazing is also described.

Description

[0001] LAMINATED GLAZING

[0002] The present invention relates to a laminated glazing for use in an automobile, in particular for use as a windscreen in an automobile; to a method of making a laminated glazing; and to sheet of glass for use in a laminated glazing.

[0003] Conventional laminated glazings for automotive windscreens comprise two plies of soda-lime- silicate glass joined by a sheet of polyvinyl butyral (PVB). Typically, each glass sheet is 2.1mm thick and the PVB sheet is typically 0.76mm thick.

[0004] As is known in the art, a laminated automotive windscreen provides the driver of the vehicle with improved safety benefits. However, vehicle manufacturers are also addressing vehicle safety in the event of a forward collision with a pedestrian.

[0005] In the event of a collision with a pedestrian, the pedestrian may impact the vehicle windscreen thereby causing further injury to the pedestrian.

[0006] W02013181505A1 describes a glass laminate including at least one chemically strengthened glass sheet with a thickness not exceeding 2.0 mm and a polymer interlayer between the glass sheets. Flaws are created in the surface of one of the glass sheets in order to weaken the glass laminate upon an impact event on a first side of the laminate, while retaining the strength of the laminate upon impact on the opposing second side of the laminate.

[0007] EP2062862A1 describes a sheet glass laminate structure produced by laminating at least three sheet glasses each having a thickness of less than 1 mm through an intermediate layer between two adjacent sheet glasses.

[0008] WO2019245819A1 describes a glass laminate construction with controlled breakage for pedestrian safety.

[0009] US2005 / 0175844A1 describes a composite pane having at least one weak point for closing a vehicle opening, which includes at least one glass pane and at least one further pane, and an intermediate layer that connects the at least one glass pane and the at least one further pane to one another. The glass pane is provided with one or more weak points such that, in an event of an object striking the composite pane, the glass pane breaks at the one or more weak points, but the vehicle opening still remains closed at least by deforming the intermediate layer of the composite pane.

[0010] US2006 / 0138798A1 describes a window including deliberate rupture zones. The window is obtained by a method whereby the glass is subjected to local overheating of the structure using a high- energy beam penetrating the glass, deliberate rupture zones are produced by sequentially guiding the beam in a predetermined path along the preferred path for the window to break along, and by sequentially focusing the beam both along the predetermined path and at various depths relative to the surface of the window.

[0011] WO2023 / 041915A1 describes a laminated glazing for a vehicle windscreen comprising first and second glass sheets joined by a sheet of adhesive interlayer material. A first region of a first major surface of the second glass sheet is spaced apart from a first region of a second opposing major surface of the second glass sheet in a thickness direction of the second glass sheet by a distance t in microns. On the first region of the second major surface of the second glass sheet is a first laser mark having a depth d in the thickness direction of the second glass sheet, wherein d in microns is at least (D x / ) / ! ()() and D is between 0.1 and 0.3.

[0012] CN117255772A discloses a method for producing a glass pane having a reduced reflection surface, in which (a) a substrate made of glass is provided, (b) the surface of the substrate is provided with a coating based on silicon oxide, and (c) at least one region of the surface of the coating facing away from the substrate is structured.

[0013] The present invention aims to provide at least an alternative laminated glazing for a vehicle windscreen that is arranged to lower the risks of serious pedestrian injuries in case the vehicle collides with a pedestrian.

[0014] Accordingly, from a first aspect the present invention provides a laminated glazing for a vehicle windscreen having a through-vision region and comprising a first sheet of glass joined to a second sheet of glass by an interlayer structure comprising at least one sheet of adhesive interlayer material, the first sheet of glass having a first major surface and an opposing second major surface; the second sheet of glass having a third major surface and an opposing fourth major surface; the laminated glazing being arranged such that the second major surface faces the third major surface; the laminated glazing having at least a first marked surface, the first marked surface being the first major surface, the second major surface, the third major surface or the fourth major surface, wherein the first marked surface has at least a first mark thereon; further wherein the first mark on the first marked surface comprises at least a first protuberant portion.

[0015] By providing a first mark having a first protuberant portion on the first marked surface, the laminated glazing has reduced strength compared to an equivalent laminated glazing not having a sheet of glass having the first marked surface.

[0016] At least the first protuberant portion of the first mark on the first marked surface is raised relative to an adjacent glass surface portion of the surface on which the first mark is on. The first protuberant portion is essentially a bulge in the surface that locally distorts the surface on which the first mark is on. The protuberant portion is not a coating on the surface on which the first mark is on. For the avoidance of doubt, if the first mark is on the first major surface, the first protuberant portion is raised relative to an adjacent surface portion of the first major surface, the adjacent surface portion of the first major surface being adjacent the first protuberant portion.

[0017] If the first mark is on the second major surface, the first protuberant portion is raised relative to an adjacent surface portion of the second major surface, the adjacent surface portion of the second major surface being adjacent the first protuberant portion.

[0018] If the first mark is on the third major surface, the first protuberant portion is raised relative to an adjacent surface portion of the third major surface, the adjacent surface portion of the third major surface being adjacent the first protuberant portion.

[0019] If the first mark is on the fourth major surface, the first protuberant portion is raised relative to an adjacent surface portion of the fourth major surface, the adjacent surface portion of the fourth major surface being adjacent the first protuberant portion.

[0020] Whilst the protuberant portion of the first mark is not formed by depositing a coating onto the respective surface, if the respective surface of the first or second glass sheet that is to be marked already has a coating thereon, in such embodiments the first mark may be on the coating and the first protuberant portion may be a bulge in the surface of the coating to locally distort the surface of the coating. However, it is preferred that the first mark is not on a coating, such as a solar control coating preferably comprising at least one electrically conductive layer.

[0021] It is well known in the art that a coating may be deposited on a major surface of a glass sheet using a physical vapour deposition method such as a sputtering method, or a chemical vapour deposition method such as an atmospheric pressure chemical vapour deposition method.

[0022] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by at least lOnm, more preferably by at least 15nm, even more preferably at least 20nm.

[0023] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by 50pm or less.

[0024] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by at most lOOOnm, more preferably by at most 900nm, even more preferably by at most 500nm, even more preferably by at most 300nm, even more preferably by at most 250nm, even more preferably by at most 200nm.

[0025] Preferably the first mark consists only of the first protuberant portion. The first protuberant portion has a first edge and a second edge spaced apart therefrom defining a width of the first protuberant portion. Preferably the width of the first protuberant portion is less than 300pm, preferably less than 200pm. Preferably the width of the first protuberant portion is at least 2pm.

[0026] Preferably the first mark on the first marked surface has a maximum dimension of 20 mm or less.

[0027] Preferably the first mark on the first marked surface has a maximum dimension of 10 pm or more.

[0028] Preferably the first mark on the first marked surface has a maximum dimension between 10 pm and 20 mm.

[0029] Preferably the first mark is in the through-vision region.

[0030] In some embodiments there is a coating, such as a solar control coating preferably comprising at least one electrically conductive layer, on the first protuberant portion, the coating having been deposited after the first protuberant portion has been formed. However, it is preferred that there is no coating deposited on the first protuberant portion after the first protuberant portion has been formed on the first marked surface.

[0031] In some embodiments the first and / or second sheet of glass has a surface compressive stress less than 100 MPa, preferably less than 75MPa, more preferably less than 50MPa, even more preferably less than 40 MPa.

[0032] Preferably the first and / or second sheet of glass has a surface compressive stress of at least 5 MPa.

[0033] Preferably the first and / or second sheet of glass has a surface compressive stress between 5 MPa and 100 MPa, or between 5 MPa and 75 MPa, or between 5 MPa and 50 MPa, or between 5 MPa and 40 MPa.

[0034] In some embodiments the first mark extends around a first region of the first marked surface, the first region of the first marked surface having a perimeter and an area inboard of the perimeter, and wherein the first protuberant portion of the first mark lies on the perimeter of the first region of the first marked surface.

[0035] By providing a first mark having a first protuberant portion that lies on the perimeter of the first region of the first marked surface, the first mark extending around the first region of the first marked surface, the laminated glazing has reduced strength compared to an equivalent laminated glazing not having a sheet of glass having the first marked surface.

[0036] At least the first protuberant portion of the first mark on the first marked surface is raised relative to an adjacent glass surface portion of the surface on which the first mark is on. The first region of the first marked surface can have any shape provided that the first region has a perimeter and an area inboard of the perimeter of the first region. As such, in these embodiments the first region is configured such the first mark does not include only a single linear line.

[0037] Preferably the area of the first region is less than 50% of the area of the glass surface on which the first mark is on.

[0038] Preferably the area of the first region is less than 50% of the area of the first major surface.

[0039] Preferably the area of the first region is less than 50% of the area of the second major surface.

[0040] Preferably the area of first region is less than 50% of the area of the third major surface.

[0041] Preferably the area of first region is less than 50% of the area of the fourth major surface.

[0042] Preferably the area of the first region is less than 10% of the area of the glass surface on which the first mark is on.

[0043] Preferably the area of the first region is less than 5% of the area of the glass surface on which the first mark is on.

[0044] Preferably the area of the first region is less than 1% of the area of the glass surface on which the first mark is on.

[0045] Preferably the area of the first region is less than 0. 1% of the area of the glass surface on which the first mark is on.

[0046] Preferably the area of the first region divided by the total area of the first marked surface is at least 5x l0’10.

[0047] Preferably the area of the first region divided by the total area of the first marked surface is at most 5 x IO-4, more preferably at most 5 x 10’5, even more preferably at most 5 x 10’6, even more preferably at most 5x l0’7.

[0048] The first protuberant portion has a first edge and a second edge spaced apart therefrom defining a width of the first protuberant portion. Preferably the width of the first protuberant portion is less than 300pm, preferably less than 200pm. Preferably the width of the first protuberant portion is at least 2pm.

[0049] Preferably the first or second edge of the first protuberant portion lies on the perimeter of the first region of the first marked surface.

[0050] Preferably a mid-point of the width of the first protuberant portion preferably lies on the perimeter of the first region of the first marked surface. As the width of the first protuberant portion becomes less, a maximum dimension of the first mark may approach a maximum dimension of the first region.

[0051] Preferably the first region of the first marked surface has a maximum dimension of 20 mm or less.

[0052] Preferably the first region of the first marked surface has a maximum dimension of 10 pm or more.

[0053] Preferably the perimeter of the first region of the first marked surface is at least 50 pm.

[0054] Preferably the perimeter of the first region of the first marked surface is at most 100 mm.

[0055] Preferably the first mark extends around the entire perimeter of the first region of the first marked surface.

[0056] Preferably the first protuberant portion extends around the entire perimeter of the first region of the first marked surface.

[0057] Preferably the first region of the first marked surface has at least one curved side.

[0058] Preferably the first region of the first marked surface is circular, elliptical, triangular or a quadrilateral.

[0059] Preferably the first region of the first marked surface is a polygon, preferably having 3 or more sides.

[0060] In some embodiments the first protuberant portion is made by a localised heat source.

[0061] Preferably the localised heat source comprises at least one of a laser, a plasma torch, a glass torch, a glass working lamp, a flame, and a heated fluid.

[0062] When the localised heat source comprises a glass torch, preferably the glass torch comprises an oxy-propane torch or an ox-acetylene torch.

[0063] In some embodiments the first protuberant portion is made by a laser such that the first protuberant portion is a first laser mark portion.

[0064] Preferably the laser has a wavelength suitable to produce the first protuberant portion.

[0065] Preferably the laser has a wavelength between 300nm and 30pm, more preferably between 300nm and 15 pm, even more preferably between 9 pm and 11 pm.

[0066] Preferably the laser is at least one of an excimer laser, an ultra-violet laser, a carbon dioxide laser, a neodymium:YAG laser and a neodymium: yttrium orthovanadate (YVCfi) laser. In some embodiments the first mark is produced using a laser such that the first mark is a first laser mark.

[0067] In some embodiments the first mark on the first marked surface is spaced apart from at least a second mark on the first marked surface by a first space.

[0068] Preferably the first space between the first mark and the second mark is at least 5mm.

[0069] Preferably the first space between the first mark and the second mark is at most 500mm.

[0070] The second mark has the same preferable features as the first mark.

[0071] Preferably the first mark on the first marked surface extends around a first region of the first marked surface, the first region of the first marked surface having a perimeter and an area inboard of the perimeter of the first region of the first marked surface, and wherein the first mark comprises at least a first protuberant portion lying on the perimeter of the first region of the first marked surface.

[0072] Preferably the second mark on the first marked surface extends around a second region of the first marked surface, the second region of the first marked surface having a perimeter and an area inboard of the perimeter of the second region of the first marked surface, and wherein the second mark comprises at least a first protuberant portion lying on the perimeter of the second region of the first marked surface.

[0073] In some embodiments the first mark on the first marked surface is one of a plurality of spaced apart marks on the first marked surface.

[0074] Each of the marks of the plurality of spaced apart marks has a nearest neighbour and is preferably spaced apart therefrom by between 5mm and 500mm.

[0075] Preferably the plurality of spaced apart marks on the first marked surface are regularly spaced. In such embodiments each of the marks of the plurality of spaced apart marks is spaced apart from a nearest neighbour by the same, or substantially the same, distance.

[0076] Preferably each of the marks of the plurality of spaced apart marks extends around a respective region of the first marked surface, the respective region having a respective perimeter and a respective area inboard of the respective perimeter.

[0077] Preferably each of the marks of the plurality of spaced apart marks comprises at least a respective first protuberant portion.

[0078] Each of the marks of the plurality of spaced apart marks have the same preferable features as the first mark. In some embodiments the first mark on the first marked surface comprises at least a second protuberant portion spaced apart from the first protuberant portion.

[0079] The second protuberant portion has the same preferable features as the first protuberant portion.

[0080] Preferably the second protuberant portion has a width that is the same as the width of the first protuberant portion.

[0081] Preferably the second protuberant portion has a length that is the same as the length of the first protuberant portion.

[0082] Preferably the second protuberant portion has a length that is less than the length of the first protuberant portion, or a length that is greater than the length of the first protuberant portion.

[0083] Preferably the second protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by the same amount as the first protuberant portion.

[0084] Preferably the second protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by between 20% and 90% of the amount that the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on. For example, if the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark by at most lOOnm, the second protuberant portion is preferably raised relative to the adjacent glass surface portion of the surface on which the first mark by at most between 20nm and 90nm.

[0085] Preferably the first protuberant portion is spaced apart from the second protuberant portion by 500pm or less.

[0086] Preferably the first protuberant portion is spaced apart from the second protuberant portion by at least 1 m or 2 pm.

[0087] The spacing of the first and second protuberant portions may be dependent upon the marking accuracy of a localised heat sources that may be used to produce the first and second protuberant portions.

[0088] In embodiments where the first mark extends around a first region of the first marked surface and wherein the first protuberant portion does not extend around the entire perimeter of the first region, the first protuberant portion has a first end and a second end. The distance along the first protuberant portion between the first and second ends thereof defines a length of the first protuberant portion.

[0089] Preferably the length of the first protuberant portion is at least 30 pm.

[0090] Preferably the length of the first protuberant portion is 10,000pm or less. A straight line connecting the first end of the first protuberant portion to the second end of the first protuberant portion has a length preferably less than 80% of the length of the first protuberant portion and / or at least 1% of the length of the first protuberant portion. The length of the straight line connecting the first end of the first protuberant portion to the second end of the first protuberant portion may be between 1% and x % of the length of the first protuberant portion, where x = 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 or 75.

[0091] In embodiments where the first mark extends around a first region of the first marked surface, the first mark on the first marked surface comprises at least a second protuberant portion spaced apart from the first protuberant portion, the second protuberant portion also lying on the perimeter of the first region of the first marked surface.

[0092] The second protuberant portion has the same preferable features as the first protuberant portion.

[0093] Preferably the second protuberant portion has a width that is the same as the width of the first protuberant portion.

[0094] Preferably the second protuberant portion has a length that is the same as the length of the first protuberant portion.

[0095] Preferably the second protuberant portion has a length that is less than the length of the first protuberant portion, or a length that is greater than the length of the first protuberant portion.

[0096] Preferably the second protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by the same amount as the first protuberant portion.

[0097] Preferably the second protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by between 20% and 90% of the amount that the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on. For example, if the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark by at most lOOnm, the second protuberant portion is preferably raised relative to the adjacent glass surface portion of the surface on which the first mark by at most between 20nm and 90nm.

[0098] Preferably the first protuberant portion is spaced apart from the second protuberant portion by 500pm or less.

[0099] Preferably the first protuberant portion is spaced apart from the second protuberant portion by at least 1 m or 2 pm. Preferably the first and second protuberant portions extend around the entire perimeter of the first region of the first marked surface. In such embodiments, there may be another space between the first and second protuberant portions, the another space being less than 10% of the perimeter.

[0100] In some embodiments the laminated glazing has a second marked surface.

[0101] In these embodiments the first marked surface is one of the first major surface, the second major surface, the third major surface and the fourth major surface, and the second marked surface is one of the other of the first major surface, the second major surface, the third major surface and the fourth major surface, the first marked surface not being the same surface as the second marked surface.

[0102] Preferably the first marked surface is the first major surface, and the second marked surface is the second major surface, the third major surface or the fourth major surface.

[0103] Preferably the first marked surface is the second major surface, and the second marked surface is the first major surface, the third major surface or the fourth major surface.

[0104] Preferably the first marked surface is the third major surface, and the second marked surface is the first major surface, the second major surface or the third major surface.

[0105] Preferably the first marked surface is the fourth major surface, and the second marked surface is the first major surface, the second major surface or the third major surface.

[0106] The second marked surface has at least a first mark thereon.

[0107] The second marked surface preferably has the same preferred features as the first marked surface.

[0108] The first mark on the second marked surface has the same preferred features as the first mark on the first marked surface.

[0109] The first mark on the second marked surface preferably extends around a first region of the second marked surface, the first region of the second marked surface having a perimeter and an area inboard of the perimeter of the first region of the second marked surface, and wherein the first mark on the second marked surface comprises at least a first protuberant portion lying on the perimeter of the first region of the second marked surface.

[0110] The first protuberant portion of the first mark on the second marked surface is raised relative to an adjacent glass surface portion of the surface on which the first mark on the second marked surface is on.

[0111] In some embodiments the laminated glazing has a second marked surface and a third marked surface. In these embodiments the first marked surface is one of the first major surface, the second major surface, the third major surface and the fourth major surface; the second marked surface is one of the other of the first major surface, the second major surface, the third major surface and the fourth major surface, the first marked surface not being the same surface as the second marked surface; and the third marked surface is one of the other of the first major surface, the second major surface, the third major surface and the fourth major surface, wherein the third marked surface is not the same as the first or second marked surfaces.

[0112] Preferably the first marked surface is the first major surface, the second marked surface is the second major surface, and the third marked surface is the third major surface or the fourth major surface.

[0113] Preferably the first marked surface is the third major surface, and the second marked surface is the fourth major surface, and the third marked surface is the first major surface or the second major surface.

[0114] The third marked surface has at least a first mark thereon.

[0115] The third marked surface preferably has the same preferred features as the first marked surface.

[0116] The first mark on the third marked surface has the same preferred features as the first mark on the first marked surface.

[0117] The first mark on the third marked surface preferably extends around a first region of the third marked surface, the first region of the third marked surface having a perimeter and an area inboard of the perimeter of the first region of the third marked surface, and wherein the first mark on the third marked surface comprises at least a first protuberant portion lying on the perimeter of the first region of the third marked surface.

[0118] The first protuberant portion of the first mark on the third marked surface is raised relative to an adjacent glass surface portion of the surface on which the first mark on the third marked surface is on.

[0119] The laminated glazing according to the first aspect of the present invention has other preferable features.

[0120] Preferably the laminated glazing is a vehicle windscreen.

[0121] Preferably the through-vision region has at least two marks therein.

[0122] Preferably the laminated glazing is curved in at least one direction. Preferably the radius of curvature in the at least one direction is between 500mm and 20000mm, more preferably between 1000mm and 8000mm.

[0123] Preferably the first major surface of the first sheet of glass is convex.

[0124] Preferably the fourth major surface of the second sheet of glass is concave. Preferably the at least one sheet of adhesive interlayer material comprises polyvinyl butyral (PVB), acoustic modified PVB, a copolymer of ethylene such as ethylene vinyl acetate (EVA), polyurethane (PU), poly vinyl chloride (PVC), a copolymer of ethylene and methacrylic acid (EMA) or a liquid curable resin.

[0125] Preferably the at least one sheet of adhesive interlayer material is a sheet of polyvinyl butyral (PVB), EVA, PVC, EMA, polyurethane, acoustic modified PVB or a liquid curable resin.

[0126] Preferably the interlayer structure comprises 2, or 3, or 4, or 5, or 6, or 7, or 8, or 9, or 10, or more, sheets of adhesive interlayer material. Each sheet of adhesive interlayer material may be the same type i.e. all PVB and may all have the same thickness.

[0127] Preferably the at least one sheet of adhesive interlayer material has a thickness between 0.3mm and 2.3mm, more preferably between 0.3mm and 1.6mm, most preferably between 0.3 and 0.8mm.

[0128] Preferably the interlayer structure comprises at least one sheet of polyester, more preferably at least one sheet of polyethylene terephthalate (PET), and preferably the at least one sheet of polyester carries on at least one major surface thereof an optically transparent coating that reflects infrared radiation.

[0129] Preferably the first sheet of glass has a thickness between 1mm and 5mm, more preferably between 1mm and 3mm, even more preferably between 1.3mm and 2.8mm, even more preferably between 1.6mm and 2.3mm.

[0130] Preferably the second sheet of glass has a thickness between 1mm and 5mm, more preferably between 1mm and 3mm, even more preferably between 1.3mm and 2.8mm, even more preferably between 1.6mm and 2.3mm.

[0131] Preferably the first sheet of glass is a sheet of soda-lime-silicate glass, in particular a sheet of float glass. Soda-lime-silicate glass is often referred to as soda-lime-silica glass, or simply a sheet “soda-lime” glass.

[0132] Preferably the second sheet of glass is a sheet of soda-lime-silicate glass, in particular a sheet of float glass.

[0133] Preferably the first and / or second sheet of glass is made using a float process, a rolled process or a down draw process.

[0134] Preferably the first and second sheets of glass are not chemically strengthened. A sheet of glass may be classified as not being chemically strengthened when the sheet of glass has not been subject to an ion exchange process or has been subject to an ion exchange process following which the depth of layer is between 0 pm and Dx pm, where Dx is 1, or 2, or 3, or 4, or 5.

[0135] In some embodiments of the first aspect of the present invention, the second sheet of glass is a sheet of alkali aluminosilicate glass. Preferably the second sheet of alkali aluminosilicate glass comprises at least about 6wt% (percent by weight) aluminium oxide (AI2O3).

[0136] In some embodiments of the first aspect of the present invention, the second sheet of glass is chemically strengthened i.e. chemically strengthened glass. When the second sheet of glazing material is chemically strengthened, preferably the second sheet of glass has a thickness less than 1 ,2mm, more preferably between 0.3mm and 1mm, even more preferably between 0.4mm and 0.9mm.

[0137] In some embodiments of the first aspect of the present invention, following an impact with a suitable impactor at an impact location on the first major surface of the first sheet of glass, the laminated glazing develops cracks in the vicinity of the impact location in less than 2ms.

[0138] In some embodiments when following an impact with a suitable impactor at an impact location on the first major surface of the first sheet of glass, the laminated glazing develops cracks in the vicinity of the impact location in less than 2ms, preferably the laminated glazing fully breaks within 2ms, more preferably 1ms of the time taken for the cracks to develop.

[0139] Preferably the impactor is as described in UN Regulation No. 127 (E / ECE / 324 / Rev.2 / Add. 126 / Rev.2).

[0140] Preferably the impactor has a mass between 3kg and 6kg, more preferably between 4kg and 5kg, even more preferably a mass of between 3.5kg and 4.5kg.

[0141] Preferably the impactor has a mass of 3.5kg or 4.5kg.

[0142] Preferably the impactor is a sphere or a spheroid and preferably has a diameter between 15cm and 20cm, more preferably between 16 and 17cm, even more preferably about 165mm.

[0143] Preferably when the impactor strikes the impact location, the velocity thereof is between 20km / h and 50km / h, more preferably between 30km / h and 45km / h, even more preferably 35km / h.

[0144] Preferably the impactor impacts the impact location by falling under gravity alone or by being propelled towards the laminated glazing to achieve a desired velocity at impact.

[0145] Preferably the time taken for the laminated glazing to break upon being impacted by the impactor is at least 50%, or 60%, or 70% or 80% shorter than the time taken for the laminated glazing to break without the laminated glazing having a first sheet of glass that has been processed in accordance with the present invention.

[0146] In some embodiments of the first aspect of the present invention, at least one of the first major surface, the second major surface, the third major surface and the fourth major surface has a coating on a least a portion thereof. Preferably the coating is adjacent the through vision region, more preferably the coating surrounds the through-vision region.

[0147] Preferably the coating is optically opaque.

[0148] Preferably the coating comprises a frit.

[0149] Preferably the frit is a type of frit used to provide an automotive glazing with an obscuration band.

[0150] Preferably the frit is suitable for application to a glass sheet using a screen-printing process. Screen printing processes are well known in the art.

[0151] Preferably the screen-printed material has a composition comprising from about 35 to about 75 weight percent frit, from about 5 to about 40 weight percent of a pigment, from zero to about 25 weight percent of a crystal seed powder, and from about 10 to about 40 weight percent of a printing medium. More preferably, the screen-printed material comprises from about 40 to about 60 weight percent frit, from about 10 to about 35 weight percent of a pigment, from zero to about 25 weight percent of a crystal seed powder, from zero to about 10 weight percent of a metal and / or a metal oxide, and from about 15 to about 40 weight of a percent printing medium.

[0152] When the frit comprises a glass frit, the frit of the screen-printed material may comprise lead- containing frit and / or lead-free frit.

[0153] Preferably the frit comprises a glass frit and / or a ceramic frit.

[0154] As used herein, the term "glass frit" means pre-fused glass material which is typically produced by rapid solidification of molten material followed by grinding or milling to a desired powder size. Preferred glass frits may comprise from 0 to about 75 weight percent lead oxide, from 0 to about 75 weight percent bismuth oxide, from 0 to about 75 weight percent silica, from 0 to about 50 weight percent zinc oxide, from 0 to about 40 weight percent boron oxide, from 0 to about 15 weight percent aluminium oxide, from 0 to about 15 weight percent zirconium oxide, from 0 to about 8 weight percent titanium oxide, from 0 to about 20 weight percent phosphorous oxide, from 0 to about 15 weight percent calcium oxide, from 0 to about 10 weight percent manganese oxide, from 0 to about 7 weight percent copper oxide, from 0 to about 5 weight percent cobalt oxide, from 0 to about 15 weight percent iron oxide, from 0 to about 20 weight percent sodium oxide, from 0 to about 20 weight percent potassium oxide, from 0 to about 15 weight percent lithium oxide and from 0 to about 7 weight percent fluoride, as well as other oxides conventionally used in glass frit compositions.

[0155] The pigment of the screen-printed material may comprise inorganic pigments such as spinels, zircons, rutiles, garnets, haematites, ultramarines, and the like may also be used as the marking component. In addition to inorganic pigments, precursors thereof are useful in forming high quality marks. For example, a light green coloured mixture of titanium dioxide, antimony trioxide and chrome oxide, which is the precursor to Cr-Sb-Ti buff, may be used.

[0156] The crystal seed powder of the screen-printed material may comprise, for example, bismuth silicate, zinc silicate and / or zinc borate.

[0157] Metal oxides include cobalt oxide, copper oxide, iron oxide and praseodymium oxide.

[0158] Suitable metal includes metal powders such as iron, copper, nickel, silver, chromium, and the like.

[0159] The present invention also provides from a second aspect a method of making a laminated glazing comprising the steps (i) providing a first sheet of glass having a first major surface and a second opposing major surface; (ii) providing a second sheet of glass having a third major surface and a fourth major surface; (iii) directing a localised heat source onto the second sheet of glass to produce a first mark on the fourth major surface, the first mark having a first protuberant portion; and (iv) laminating the first sheet of glass to the second sheet of glass using an interlayer structure comprising at least a first adhesive interlayer.

[0160] Preferably the localised heat source comprises at least one of a laser, a plasma torch, a glass torch, a glass working lamp, a flame, and a heated fluid, preferably heated gas such as air.

[0161] Preferably the first mark extends around a first region of the fourth major surface, the first region of the fourth major surface having a perimeter and an area inboard of the perimeter, the first protuberant portion of the first mark lying on the perimeter of the first region of the fourth major surface.

[0162] Preferably the first region of the fourth major surface is a predetermined first region on the fourth major surface, wherein step (iii) includes providing a control sequence to direct the localised heat source onto the second sheet of glass to follow a path defined by the predetermined first region on the fourth surface to produce the first mark on the fourth major surface.

[0163] Preferably the path followed by the localised heat source to produce the first mark on the fourth major surface corresponds to at least a portion of the perimeter of the first region on the fourth major surface.

[0164] Preferably the first protuberant portion of the first mark on the fourth surface has a first end spaced apart from a second end, and the distance along the first and second ends of the first protuberant portion of the first mark on the fourth surface defines a length of the first protuberant portion on the fourth surface.

[0165] Preferably the length of the first protuberant portion is at least 30 pm.

[0166] Preferably the length of the first protuberant portion is 10,000pm or less. Preferably the localised heat source scans over the second sheet of glass at a scan speed, wherein the scan speed is selected such that a protuberant portion is formed on the fourth major surface of the second sheet of glass.

[0167] Preferably the scan speed is at least 5mm / s, more preferably at least 50mm / s.

[0168] Preferably the scan speed is at most 10,000mm / s, more preferably at most 2000mm / s.

[0169] Preferably the localised heat source has a power density less than 10 kW / mm2.

[0170] Preferably the localised heat source has a power density less than 5 kW / mm2.

[0171] Preferably the power density of the localised heat source is less than 1 kW / mm2, more preferably less than 0.5 kW / mm2, even more preferably less than 0.3 kW / mm2.

[0172] Preferably the power density of the localised heat source is at least 0.01 kW / mm2, more preferably at least 0.05 kW / mm2, even more preferably at least 0.09 kW / mm2.

[0173] In some embodiments of the second aspect of the present invention, the localised heat source is a laser beam from a laser. In these embodiments the first mark is a first laser mark.

[0174] The first laser mark on the first region of the fourth major surface is produced by directing a suitable laser beam having sufficient power for a sufficient length of time towards the third or fourth major surface of the second sheet of glass to produce the first laser mark.

[0175] Preferably the first laser mark on the first region of the fourth major surface is produced by directing a suitable laser beam having sufficient power for a sufficient length of time towards the fourth major surface of the second sheet of glass to produce the first laser mark.

[0176] Preferably the power density of the laser beam is selected such that the laser does not damage the glass surface by causing cracking on the surface and / or in the body of the second sheet of glass.

[0177] Preferably the first laser mark is produced by scanning the laser beam over the fourth major surface at a scan speed sufficient to produce the first protuberant portion.

[0178] Preferably the scan speed is between 5mm / s and 10,000mm / s, more preferably between 50mm / s and 5000mm / s.

[0179] Preferably the laser beam has a wavelength between 300nm and 30pm, more preferably between 300nm and 15 pm, even more preferably between 9 pm and 11 pm.

[0180] Preferably the laser is at least one of an excimer laser, an ultra-violet laser, a carbon dioxide laser, a neodymium:YAG laser and a neodymium: yttrium orthovanadate (YVCfi) laser. Preferably the laser is a continuous laser or a pulsed laser.

[0181] During step (iii), preferably the laser beam has a circular spot shape on the first major surface of the first sheet of glass.

[0182] Preferably the laser beam has a spot diameter less than 1mm, preferably less than 500 pm. If the spot is circular, the maximum external dimension is the diameter of the spot.

[0183] Preferably the laser beam has a spot diameter of more than 20 pm.

[0184] Preferably the laser beam has a spot diameter between 50 pm and 250 pm.

[0185] Preferably the laser beam has a power density suitable to produce the protuberant portion without producing any cracking of the first sheet of glass, which may be surface cracking and / or cracking between the first and second major surfaces of the first sheet of glass.

[0186] Preferably the laser beam has a power density less than 10 kW / mm2.

[0187] Preferably the laser beam has a power density less than 5 kW / mm2.

[0188] Preferably the power density of the laser beam is less than 1 kW / mm2, more preferably less than 0.5 kW / mm2, even more preferably less than 0.3 kW / mm2.

[0189] Preferably the power density of the laser beam is at least 0.01 kW / mm2, more preferably at least 0.05 kW / mm2, even more preferably at least 0.09 kW / mm2.

[0190] In some embodiments of the second aspect of the present invention, at least one of the first major surface of the first sheet of glass, the second major surface of the first sheet of glass and the third major surface of the second sheet of glass has on at least a portion thereof a coating, preferably a solar control coating layer, and / or an obscuration band.

[0191] In some embodiments of the second aspect of the present invention, the fourth major surface of the second sheet of glass has on a least a portion thereof a coating, preferably a solar control coating, and the first protuberant portion is formed in the coating.

[0192] In some embodiments of the second aspect of the present invention a coating, preferably a solar control coating preferably comprising at least one electrically conductive layer, is deposited on the at least the first protuberant portion after the first protuberant portion has been formed.

[0193] In some embodiments of the second aspect of the present invention, step (iii) takes place before step (iv). Preferably following step (iv) the second major surface of the first sheet of glass faces the third major surface of the second sheet of glass. In such embodiments, the fourth major surface of the second sheet of glass corresponds to surface one of the laminated glazing or surface four of the laminated glazing.

[0194] Preferably following step (iv) the fourth major surface of the second sheet of glass faces the first adhesive interlayer. In such embodiments, the fourth major surface of the second sheet of glass corresponds to surface two of the laminated glazing or surface three of the laminated glazing.

[0195] In some embodiments of the second aspect of the present invention, step (iv) takes place before step (in).

[0196] In these embodiments, following step (iv) preferably the fourth major surface of the second sheet of glass is surface one of the laminated glazing.

[0197] In these embodiments, following step (iv) preferably the fourth major surface of the second sheet of glass is surface four of the laminated glazing.

[0198] In some embodiments, the method comprises a heating step before the marking step (iii), wherein the heating step comprises heating the first and / or second sheet of glass to a temperature suitable for shaping thereof, preferably between 580°C and 680°C.

[0199] After the first and / or second glass sheet has been heated to a temperature suitable for shaping, preferably the heated glass sheet or sheets is shaped using a shaping step.

[0200] Preferably the shaping step comprises supporting the first and / or second sheet of glass on a shaping member.

[0201] Preferably the shaping step comprises shaping the first and / or second sheet of glass by sagging under gravity and / or pressing between a pair of shaping members having complementary shaping surfaces.

[0202] Preferably following the shaping step the first sheet of glass is shaped such that the first major surface of the first sheet of glass is a convex surface.

[0203] Preferably following the shaping step the second sheet of glass is shaped such that the fourth major surface of the second sheet of glass is a concave surface.

[0204] Preferably the second sheet of glass is bent at the same time as the first sheet of glass. In such embodiments, the first sheet of glass and the second sheet of glass are preferably a nested pair.

[0205] Preferably following the shaping step, the method includes a step of cooling the shaped glass sheet to ambient conditions, typically below 50 °C. After the first and / or second sheet of glass has been shaped, the shaped glass sheet or sheets is marked during the marking step (iii).

[0206] In some embodiments of the second aspect of the present invention, the first and second glass sheets are curved and form a congruent pair, and wherein step (iii) takes place after step (iv).

[0207] The present invention also provides from a third aspect a sheet of glass for a vehicle windscreen, the sheet of glass having a first major surface and a second opposing major surface, there being on the first major surface of the sheet of glass at least a first mark, and wherein the first mark comprises at least a first protuberant portion.

[0208] The first protuberant portion is raised relative to an adjacent glass surface portion of the first major surface.

[0209] The first protuberant portion is essentially a bulge in the surface that locally distorts the surface on which the first mark is on. The first protuberant portion is not formed by depositing a coating on the surface on which the first mark is on.

[0210] Whilst the first protuberant portion is not formed by depositing a coating onto the first major surface of the sheet of glass, if the first major surface of the sheet of glass has a coating thereon, the first protuberant portion may be a bulge in the surface of said coating to locally distort the surface of said coating.

[0211] However, it is preferred that the first mark on the first major surface the sheet of glass is not on a coating, such as a solar control coating preferably comprising at least one electrically conductive layer.

[0212] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the first major surface by at least lOnm, even more preferably at least 15nm or 20nm.

[0213] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the first major surface by 50pm or less.

[0214] Preferably the first protuberant portion is raised relative to the adjacent glass surface portion of the surface on which the first mark is on by at most lOOOnm, more preferably by at most 900nm, even more preferably by at most 500nm, even more preferably by at most 300nm, even more preferably by at most 250nm, even more preferably by at most 200nm.

[0215] Preferably the first mark extends around a first region of the first major surface of the first sheet of glass, the first region of the first major surface of the sheet of glass having a perimeter and an area inboard of the perimeter of the first region of the first major surface, and wherein the first protuberant portion lies on the perimeter of the first region of the first major surface of the sheet of glass. Preferably the first mark on the first major surface is one of a plurality of spaced apart marks on the first major surface.

[0216] Each of the marks of the plurality of spaced apart marks has a nearest neighbour and is preferably spaced apart therefrom by between 5mm and 500mm.

[0217] Preferably the plurality of spaced apart marks on the first marked surface are regularly spaced. In such embodiments each of the marks of the plurality of spaced apart marks is spaced apart from a nearest neighbour by the same, or substantially the same, distance.

[0218] Preferably each of the marks of the plurality of spaced apart marks extends around a respective region of the first major surface, the respective region having a respective perimeter and a respective area inboard of the respective perimeter.

[0219] Preferably each of the marks of the plurality of spaced apart marks comprises at least a respective first protuberant portion.

[0220] Preferably the first protuberant portion of each respective mark of the plurality of spaced apart marks is raised relative to a respective adjacent glass surface portion of the first major surface by an amount between lOnm and 50 pm.

[0221] Preferably the first protuberant portion of each respective mark of the plurality of spaced apart marks is raised relative to a respective adjacent glass surface portion of the first major surface by the same amount.

[0222] Preferably the sheet of glass has a thickness between 1mm and 5mm, more preferably between 1mm and 3mm, even more preferably between 1.3mm and 2.8mm, even more preferably between 1.6mm and 2.3mm.

[0223] Preferably the sheet of glass is curved in at least one direction. Preferably the radius of curvature in the at least one direction is between 500mm and 20000mm, more preferably between 1000mm and 8000mm.

[0224] Preferably the sheet of glass comprises at least one coated region on the first and / or second major surface thereof, preferably wherein the coating comprises a frit, in particular a type of frit used to provide an automotive glazing with an obscuration band.

[0225] Preferably the sheet of glass has a soda-lime-silicate composition.

[0226] Preferably the sheet of glass has a surface compressive stress less than 100 MPa, preferably less than 75MPa, more preferably less than 50MPa, even more preferably less than 40 MPa.

[0227] Preferably the sheet of glass has a surface compressive stress of at least 5 MPa. Preferably the sheet of glass has a surface compressive stress between 5 MPa and 100 MPa, or between 5 MPa and 75 MPa, or between 5 MPa and 50 MPa, or between 5 MPa and 40 MPa.

[0228] Preferably the sheet of glass has at least two spaced apart edges, the spacing thereof preferably being at least 50cm, more preferably at most 300cm.

[0229] In some embodiments of the third aspect of the present invention, a coating, preferably a solar control coating preferably comprising at least one electrically conductive layer, is on the first protuberant portion.

[0230] In such embodiments, the coating is deposited on the first protuberant portion after the first protuberant portion has been formed. The coating preferably covers at least a portion of the first major surface of the sheet of glass and the first protuberant portion.

[0231] In some embodiments of the third aspect of the present invention, the sheet of glass has an obscuration band on at least a portion of at least one of the first and second major surfaces of the sheet of glass.

[0232] In some embodiments of the third aspect of the present invention, the sheet of glass has a coating, such as a solar control coating preferably comprising at least one electrically conductive layer on at least a portion of the second major surface.

[0233] In some embodiments of the third aspect of the present invention, the sheet of glass has an obscuration band on at least a portion of at least one of the first and second major surfaces of the sheet of glass.

[0234] In some embodiments of the third aspect of the present invention, the sheet of glass was made using a float process such that the sheet of glass has a tin-side and an air-side.

[0235] Preferably the first major surface is the air-side.

[0236] Preferably the first major surface is the tin-side.

[0237] Preferably the first protuberant portion is on the air-side or the tin-side and a coating is on the first protuberant portion such that the coating is in direct contact with the first protuberant portion.

[0238] In some embodiments of the third aspect of the present invention, the first major surface of the sheet of glass has a coating on at least a portion thereof, and the first mark is on the coating such that the first protuberant portion is in the coating. After the first mark has been formed, another coating may be deposited on at least the first protuberant portion.

[0239] In such embodiments, the coating on the first major surface of the sheet of glass may be referred to a first coating and the coating deposited on at least the first protuberant portion after the first mark has been made may be referred to as a second coating. That is, in such embodiments the first major surface of the sheet of glass has a first coating on at least a portion thereof, and the first mark is on the first coating; and a second coating is on the first protuberant portion and preferably in direct contact therewith.

[0240] The present invention will now be described with reference to the following figures (not to scale) in which:

[0241] Figure 1 is a cross-sectional view of a laminated glazing in accordance with the present invention;

[0242] Figure 2 is a plan-view of a laminated glazing in accordance with the present invention;

[0243] Figure 3 is a Nomarski interference contrast (NIC) microscope image of a laser mark;

[0244] Figure 4 is a plan view schematic of the image shown in figure 3 extending around a first region;

[0245] Figure 5 is a representation of the laser mark of figure 3 extending around a second region;

[0246] Figure 6 is a representation of the laser mark of figure 3 extending around a third region ;

[0247] Figure 7 is a graph showing the surface profile of a region of a glass surface with a laser mark as shown in figure 3 thereon;

[0248] Figure 8 is a plan view representation of another laser mark on a glass surface;

[0249] Figure 9 is a plan view representation of another laser mark on a glass surface;

[0250] Figure 10 is a schematic isometric view of the laser mark shown in figure 9 on a sheet of glass;

[0251] Figure 11 is a schematic of apparatus used to laser mark a sheet of glass in accordance with the present invention;

[0252] Figure 12 is a schematic isometric view of a sheet of glass with two laser marks on a surface thereof; cross-sectional view of another laminated glazing in accordance with the present invention;

[0253] Figure 13 is a plan view of a sheet of glass having an array of laser marks thereon for making strength measurement;

[0254] Figures 14-17 are schematic plan view representations of different laser marks having at least a first protuberant portion;

[0255] Figure 18 is the view from inside a vehicle that has a windscreen in accordance with the present invention; and Figure 19 is a schematic cross-sectional representation of a method to test the breakage properties of a vehicle windscreen of the type shown in figures 1 and 2.

[0256] Figure 1 shows a cross-sectional view of a curved laminated glazing in accordance with the present invention.

[0257] The laminated glazing 1 has a first sheet 3 of soda-lime-silicate glass having a composition such as clear float glass and may include colouring agents such as iron oxide to provide the laminated glazing with some form of solar control. The first sheet 3 has a thickness of 2. 1mm although the thickness may be in the range 1.4mm to 4.0mm or in the range 1.6mm to 2.3mm.

[0258] A typical soda-lime-silicate glass composition is (by weight), SiO269 - 74 %; AI2O3 0 - 3 %; Na2O 10 - 16 %; K2O 0 - 5 %; MgO 0 - 6 %; CaO 5 - 14 %; SO3 0 - 2 %; Fe2O30.005 - 2 %. The glass composition may also contain other additives, for example, refining aids, which would normally be present in an amount of up to 2 %. The soda-lime-silica glass composition may contain other colouring agents such as CO3O4, NiO and Se to impart to the glass a desired colour when viewed in transmitted light. The transmitted glass colour may be measured in terms of a recognised standard such as BS EN410 (2011).

[0259] As is known in the art, when glass is made using a float process, where molten glass is formed into a ribbon on the surface of a bath of molten tin, glass that has been in contact with the molten tin is referred to as the “tin-side” and the opposite side is referred to as the “air-side”. Sheets of glass produced by such a float process therefore have a tin-side and an air-side. The tin-side has a higher content of tin oxide in the glass surface and may be identified by using suitable X-ray analysis of the glass surface.

[0260] A coating such as a solar control coating, may be deposited on the tin-side or the air-side of a glass sheet that has produced using a float process. It is well known in the art that such a coating may be deposited using a physical vapour deposition method such as a sputtering method, or a chemical vapour deposition method such as an atmospheric pressure chemical vapour deposition method.

[0261] It is known that a coating such as an obscuration band may be printed i.e. screen printed, onto the air-side or tin-side of a glass sheet that has been produced using a float process.

[0262] The laminated glazing 1 also has a second sheet 7 of soda-lime-silicate glass having a thickness of 2.1mm, but the second sheet may have a thickness may be in the range 1.4mm to 4.0mm and is preferably not as thick as the first sheet 3.

[0263] The first sheet 3 is joined to the second sheet 7 by an adhesive interlayer structure 5. The adhesive interlayer structure 5 in this example is a 0.76mm thick sheet of PVB. The adhesive interlayer 5 may have a thickness between 0.3mm and 1.8mm.

[0264] Other suitable adhesive interlayers include PVC, EVA, EMA, and polyurethane. The interlayer structure 5 may comprise two or more sheets of adhesive interlayer material. The interlayer structure may comprise two sheets of adhesive interlayer material with a sheet of non-adhesive interlayer material such as PET therebetween.

[0265] The laminated glazing 1 is curved in one or more directions. The radius of curvature in one of the one or more directions is between 1000mm and 8000mm.

[0266] When the laminated glazing is curved in two directions, suitably each direction of curvature is orthogonal to the other. Suitably the radius of curvature in one or both directions of curvature is between 1000mm and 8000mm.

[0267] The first sheet 3 has a convex first major surface 9 and an opposing concave second major surface 11. The second sheet 7 has a convex first major surface 13 and an opposing concave second major surface 15. The concave surface 11 of the first sheet 3 is in contact with the adhesive interlayer 5 and the convex surface 13 of the second sheet 7 is in contact with the adhesive interlayer 5. Using conventional nomenclature, the convex major surface 9 of the first sheet 3 is “surface one” (or SI) of the laminated glazing 1, the concave major surface 11 of first sheet 3 is “surface two” (or S2) of the laminated glazing 1, the convex major surface 13 of second sheet 7 is “surface three” (or S3) of the laminated glazing 1 and the concave major surface 15 of second sheet 7 is “surface four” (or S4) of the laminated glazing 1.

[0268] There is an array of laser marks 17 on surface four (the concave major surface 15 of the second sheet 7 of soda-lime-silicate glass).

[0269] Each laser mark in the array of laser marks 17 has a respective protuberant portion, the protuberant portion being raised relative to an adjacent portion of surface four. Each respective protuberant portion is a bulge in surface four that has a curved shape as shall be discussed in more detail hereinafter.

[0270] Figure 2 is a schematic plan-view of the laminated glazing 1 viewed in the direction of arrow 10 of figure 1.

[0271] In figure 2, the periphery of the laminated glazing is typical of a vehicle windscreen. The laminated glazing has a lower peripheral edge 19. In this example an obscuration band 21 is on the concave major surface 15 of the second sheet 7. The obscuration band is optically opaque and was applied to the glass in a conventional manner prior to the second sheet 7 being shaped. The obscuration band 21 is a coating that was screen-printed onto the glass surface and is fused onto the glass surface by heating.

[0272] Inboard of the obscuration band 21 the laminated glazing 1 has a through-vision region 23. In the art, the allowable light transmission of a vehicle windscreen is usually set by legislation. In this example, the through vision region exhibits a total visible light transmittance (Illuminant A, two-degree observer) of 70% or more as measured at normal incidence in accordance with a recognized standard such as BS EN410 (2011). In this example the array of laser marks 17 is located in the through-vision region 23. Each laser mark in the array of laser marks 17 has substantially the same shape in plan-view and has a first protuberant portion that in plan-view is in the shape of a letter “C” (which may also be referred to as an “open circle”). In this example, the laser marks are arranged in rows (of which in this example there can be seen to be four), with each laser mark in a particular row being uniformly spaced from its nearest neighbour along the row. Subsequent rows are spaced apart in a parallel arrangement and in this example the laser marks are offset to lie in the space below the two nearest laser marks of the adjacent upper (when present) and lower (when present) row.

[0273] The laser marks in one row are labelled as 17a, 17b, 17c and 17e and these correspond to the laser marks shown in the array 17 of figure 1 i.e. figure 1 is a view along the plane perpendicular to the line m-nf of figure 2. As can be seen the laser marks 17a, 17b, 17c and 17e lie along the line (or axis) m-nf .

[0274] By providing the laser marks 17a, 17b, 17c, 17d, 17e in the through vision-region 23, in the event of an impact on the convex first major surface 9 of the first sheet 3, the second sheet 7 can break more easily because the strength thereof has been reduced, allowing the laminated glazing 1 to break more easily. When the laminated glazing 1 is installed as a windscreen in a vehicle, in the event of a pedestrian being involved in a collision with the vehicle, the reduction in strength of the windscreen allows the windscreen to break more easily upon an impact with the convex first surface 9 to reduce the potential seriousness of injury to the pedestrian.

[0275] Although the laser marks 17a, 17b, 17c, 17d, 17e are positioned in the through-vision region 23, the size of each laser mark is small compared to the area of the through vision region 23, typically having a maximum dimension in plan-view of about 0.3mm, this feature contributing to make the laser mark not easily visible to the driver of the vehicle.

[0276] Furthermore, the power density used to make each laser mark 17a, 17b, 17c, 17d, 17e was selected so that the visible perception of said laser marks was as low as possible whilst still affecting the strength of the glass sheet.

[0277] If the power density of the laser used to create the array of laser marks 17 is too high, cracking may be observed which makes the laser mark more visible in the laminated glazing. Cracking may also affect the strength of the laminated glazing during routine handling and / or use, for example during installation and / or during stone impact tests. It is thought such cracking may be related to thermal shock, which may be avoided by using a suitably low power density for the laser, but where the power density is still high enough to produce the protuberant portions associated with each respective laser mark in the array 17.

[0278] Similarly ablation of the surface may give rise to increased visibility of the laser mark, and this may be more prevalent if laser marking a coated glass surface. Laser marks made in accordance with the present invention are difficult to see by the unaided eye making them suitable for positioning in the through-vision region, thereby allowing more of the glass sheet to be provided with laser marks to assist with a reduction in strength of the laminated glazing 1.

[0279] The orientation of the laser marks in each row does not have to be the same, for example one laser mark could be orientated with the opening of the letter “C” facing to the right, whereas an adjacent laser mark in the same row could be orientated such that the opening of the letter “C” faces upwards, or downwards, or to the left. It may be desirable to orientate the laser marks in the same way, but this is not essential given the laser marks cannot be seen by the unaided human eye or are difficult to see by the unaided human eye.

[0280] Each laser mark 17a, 17b, 17c, 17d, 17e was produced by directing a suitable laser beam towards the concave major surface 15 using a low power so as not to produce cracking or ablation. The laser produces a laser mark having a protuberant portion which is raised relative to the adjacent glass surface. For each laser mark 17a, 17b, 17c, 17d, 17e the respective protuberant portion was raised relative to the adjacent glass surface by about the same amount, typically between 50 - 150 nm. It is preferred that all the laser marks have substantially the same height protuberant portion. The low height of the protuberant portion also helps reduce the visibility of the laser marks. The height of the protuberant portion may be adjusted by using a different power density for the laser and / or a different wavelength of laser which may be absorbed in the glass at a different depth.

[0281] The laser marks in the array 17 may be made on the concave surface 15 of the laminated glazing 1 after the first and second sheets 3, 7 thereof have been laminated together. Alternatively, the laser marks in the array 17 may be made on the second sheet of glass 7 before being laminated to the first sheet of glass 3. This may be before or after the second sheet of glass has been shaped using a shaping process.

[0282] Figure 3 shows a Nomarski interference contrast (NIC) microscope image of one of the laser marks 17a. The other laser marks in the array 17 have a similar NIC microscope image to that shown in figure 3.

[0283] The laser mark 17a is in the form of a letter “C” (or “open circle”) having a protuberant portion 31. The protuberant portion 31 is raised with respect to the adjacent surface portion 33 i.e. the glass surface not treated with the laser beam.

[0284] A schematic of the image shown in figure 3 is provided as figure 4.

[0285] Reference to figures 3 and 4 shows how the laser mark 17a extends around a region 35 on the surface 15 of the second sheet of glass 7. In this example the region 35 is circular having a perimeter 36 and an area 37 inboard of the perimeter 36. The protuberant portion 31 lies on the perimeter 36 of the region 35.

[0286] The circular region 35 has a diameter 38 of about 0.25mm. This is the maximum dimension of the region 35. The protuberant portion 31 has an outer edge region 3 la and an inner edge region 3 lb. The spacing of the outer and inner edge regions 3 la, 3 lb defines a width 32 of the protuberant portion 31. The width 32 is substantially constant along the protuberant portion 31, although there may be a slight variation of the width along the protuberant portion i.e. less than 25% variation.

[0287] In this example the protuberant portion 31 has a width 32 of about 70 pm. Given that the width of the protuberant portion 31 is non-zero, the maximum dimension of the laser mark 17a is greater than the maximum dimension of the region 35. However, depending upon the precise shape of the region on which the protuberant portion 31 lies, and which particular part of the protuberant portion lies of the perimeter of this region, the maximum dimension of the laser mark may be the same as the maximum dimension of the protuberant portion. This is discussed in more detail with reference to figures 5 and 6.

[0288] In this example of figures 3 and 4, the protuberant portion 31 does not extend around the entire perimeter of the region 35 so the protuberant portion 31 has a first end A and a second end A

[0289] The distance along the protuberant portion 31 between the points A and A" defines the length of the protuberant portion. Between the points A and A" there is no protuberant portion (so there is no protuberant portion that lies on the perimeter of the region 35 in between points A and A ’).

[0290] The first end A is a starting end of the protuberant portion 31 and the second end A ’ is a finishing end of the protuberant portion 31. The first and second ends A, A ’ lie on the perimeter 36 of the circular region 35.

[0291] Instead of a minor arc connecting the first and second ends A, A ’ to form region 35, there may be a straight line connecting the first and second ends A, A" to form region 35.

[0292] In this example the protuberant portion 31 extends around about 70% of the perimeter of the region 35 such that the length of the protuberant portion is about 0.55mm. If a straight line (not lying on the protuberant portion 31) joins the first and second ends A, A ’, the length thereof is about 0.23mm.

[0293] With reference to figures 4 and 5, figure 5 shows the protuberant portion 31 with the inner edge 3 lb thereof aligned with a region 45 that is substantially circular. The laser mark 17a is shown extending around the region 45 and the protuberant portion 31 lies on the perimeter of the region 45. Since the laser mark 17a is a letter “C”, between the points B-B ’ there is no inner edge of the protuberant portion and the region between the points B-B ’ is shown as being curved (solid black line B-B ’), being an interpolation of the perimeter of the region 45 which is aligned with the inner edge region 3 lb. Instead of being curved, the curved solid black line B-B ’ may be replaced with a straight line connecting the points B-B ’ (shown as straight dotted line B-B1), in which case the region so formed would have a smaller area enclosed by the perimeter of said region. With reference to figures 4 and 6, figure 6 shows the protuberant portion 31 with the outer edge 3 la thereof aligned with a region 55 that is substantially circular. The laser mark 17a is shown extending around the region 55 and the protuberant portion 31 lies on the perimeter of the region 55. Since the laser mark 17a is an “open circle”, between the points C-C ’ there is no outer edge of the protuberant portion and the region between the points C-C ’ is shown as being curved (solid black line C-C ’), being an interpolation of the perimeter of the region 55 which is aligned with the outer edge region 3 la. Instead of being curved, the curved solid black line C-C ’ may be replaced with a straight line connecting the points C-C ’ (shown as straight dotted line C-C), in which case the region so formed would have a smaller area enclosed by the perimeter of said region.

[0294] When the protuberant portion does not extend around the entire region (for example as shown in figures 3 and 4), it is preferred that the perimeter of the region contains a linear section connecting the ends of the perimeter of the region on which the protuberant portion lies, for example as shown in figures 5 and 6.

[0295] The amount the protuberant portion 31 is raised relative to the adjacent glass surface may be determined using a commercially available surface profiler such as a Bruker Dektak® XT Stylus Profiler (see www.bruker.com). The results of a surface profile scan using such equipment across the line P-P" shown in figure 3 are shown in figure 7.

[0296] In figure 7, the axis 61 is a lateral displacement across the glass surface being measured, in millimetres (mm) and the axis 63 is the height of the surface above the reference surface in nanometres (nm).

[0297] The region 65 of the graph is representative of the adjacent surface portion 33 of the glass sheet where there is no laser mark (so the height above the reference surface should be zero).

[0298] As figure 7 shows, across the line P-P" there are two raised portions with a first raised portion centred around 0.10mm and a second raised portion centred around 0.35mm. The peak 67 of the first raised portion is at 0.10mm and the peak 69 of the second raised portion is at 0.35mm. The separation of the peaks 67, 69 is therefore 0.25mm. This corresponds to the diameter 38 of the region 35 shown in figure 4.

[0299] The full width half maximum (FWHM) of the first and second raised portions is about 0.05mm (50pm).

[0300] In this example the protuberant portion 31 therefore has an average height of about 55 nm. Multiple scans across different parts of the protuberant portion 31 may be used to determine the average height of the protuberant portion.

[0301] Each peak is substantially Gaussian-like, illustrating how the protuberant portion is a curved portion of the surface relative to the adjacent surface. Figure 8 shows a plan view representation of another laser mark 170 on a surface of a sheet of glass. The laser mark 170 is similar to the laser mark 17a previously described and is also in the form of an “open circle”, or letter “C”. In contrast to the laser mark 17a, the laser mark 170 has a protuberant portion 131 that extends about 60% around the perimeter of the region 35. Given that the region 35 is circular having a diameter of 0.25mm, the protuberant portion 131 has a length between the points D and D ’ of about 0.47mm. The straight (dotted) line connecting the points D and D ’ therefore has a length of about 0.31mm.

[0302] The solid line connecting the points D and D ’ is a minor arc of the circular region 35.

[0303] Figure 9 shows a plan view representation of another laser mark 270 on a surface of a sheet of glass 272 (not shown in figure 9). A schematic isometric representation of the laser mark 270 on the surface 274 of the glass sheet 272 is shown in figure 10.

[0304] With reference to figures 9 and 10, the laser mark 270 is similar to the laser mark 17a in that it extends around a region 35 having the same dimensions as previously described. However, in contrast to the laser mark 17a, the laser mark 270 has four protuberant portions 231a, 23 lb, 231c and 23 Id. Each protuberant portion lies on the perimeter of the region 35.

[0305] The first protuberant portion 23 la is longer than the protuberant portions 23 lb, 231c and 23 Id.

[0306] The second protuberant portion 23 lb is longer than the protuberant portions 231c and 23 Id.

[0307] The third protuberant portion 231c is longer than the protuberant portion 23 Id.

[0308] Each of the protuberant portions 23 la, 23 lb, 231c and 23 Id are raised relative to an adjacent portion of the major surface 274 of the glass sheet 272.

[0309] Figure 11 shows a schematic of an apparatus used to mark a surface of a sheet of glass with a localised heat source. In this example the localised heat source is a laser beam from a laser. Suitable apparatus is commercially available to laser mark materials, including glass, from Keyence (UK) Ltd, see for example www.keyence.co.uk.

[0310] Lasers are also known to provide laser marks on coated glass substrates that may have higher reflectivity than uncoated glass sheets.

[0311] In the example shown in figure 11 the apparatus 300 was provided by a Keyence ML-Z9610 Laser Marker (which has a 10.6 pm wavelength CO2 laser with a spot size of 140 pm and maximum power density of about 2kW / mm2).

[0312] The apparatus 300 includes a laser 302, a control system 304 and a marking head 306. The laser is a CO2 laser having a wavelength of 10.6 pm and a maximum power output of 30W. The laser 302 produces laser beam 303. The control system 304 is used to control the laser and the power thereof via suitable cabling 305. The marking head 306 has at least one reflective surface 308 and is used to deflect the laser beam 303 to provide a desired path for the laser beam to follow to mark a surface of a material.

[0313] In this example the material to be marked is a sheet of soda-lime-silica glass 310 made using the float process, wherein molten glass is formed into a sheet on the surface of a pool of molten tin. The glass surface that has been in contact with the molten tin is referred to in the art as the “tin-side” and the opposite surface is referred to as the “air-side”. The sheet of soda-lime-silica glass 310 has a first major surface 312 and an opposing second major surface (not labelled). Neither the first major surface 312 nor the second major surface had a coating thereon. The first major surface 312 in this example is the tin-side and the apparatus 300 is used to mark the first major surface 312. The apparatus could also be used to mark the airside if desired, instead of, or as well as, marking the tin-side.

[0314] The control system 304 includes a computer and is used to control the marking head 306. Control signals from the control system 304 are provided to the marking head 306 via suitable cabling 307. The control system is programmed with a desired path for the deflected laser beam 303’ to follow. In this example, the desired path is a circle 314 on the first major surface 312. The deflected laser beam 303’ strikes the first major surface 312 as a circular spot 316 with a spot size (diameter) of about 140 pm and the marking head 306 deflects the laser beam 303 along the desired circular path 314.

[0315] There may be a power distribution across the laser spot diameter, such as a Gaussian profile, such that the power density at the glass surface is different at different parts of the laser spot. With reference to figures 3, 4 and 7, the laser beam had a spot diameter of about 140 pm but the width 32 of the protuberant portion is only about 70 pm, illustrating that the power density at a central portion of the laser spot is more concentrated and therefore able to sufficiently heat the glass to produce the protuberant portion, but not so at the edges of the spot.

[0316] The laser mark 17a of figure 3 was made using the apparatus 300 as previously described with a scan speed along a desired circular path of 300mm / s. Given the diameter of the circles was set at 0.25mm, the circumference is about 0.79mm such that each circular path was completed in about 2.6 ms.

[0317] Depending upon the power density used, and the scan speed, cracking of the glass sheet may be observed instead of (or as well as) the formation of a protuberant portion of the first major surface 312. Cracking is not desirable because this may cause the laser marks to become visible. Also, cracking may induce additional cracking over time, with crack lengths becoming more easily visible to the unaided human eye.

[0318] It was found that using a scan speed of 300mm / s, the Keyence ML-Z9610 Laser Marker at a power density of about 0.15kW / mm2along a circular path of diameter 0.25mm could formed a laser mark having a protuberant portion on the tin-side of a sheet of soda-lime-silica glass without any evidence of cracking. A NIC image of one such laser mark is shown in figure 3.

[0319] In the unrelated technical field of glass substrates for data recording disks, it is known from US5,567,484 that a glass surface may be provided with “bumps” without unwanted micro-cracking by limiting the laser power to a value in a narrow operating region below an abrupt thermal shock power threshold. In US5,567,484 this process was used to create surface textures in a glass surface. Smooth “bumps” were formed that reduced stiction in a contact start-stop region of a data storage disk. In US5,567,484 it was thought that the “bumps” may result from a relaxation of surface stress caused by the laser induced surface softening or by the laser induced thermal expansion that “freezes-in” as the surface cools below the softening point.

[0320] Without being bound by theory, assuming a similar mechanism as described in US5,567,484, the scan speed will have an effect on the protuberance formation. This can be evaluated by measuring the protuberant portion formed for different scan speeds and / or different power densities. The laser wavelength may also be adjusted to obtain more efficient absorption in the glass sheet.

[0321] An advantage of the present invention is that the protuberant portion of each laser mark is not accompanied by any, or any observable, micro-cracking such that the general stability of the glass sheet (during handling, installation etc) is not compromised. Also, the absence of micro-cracking reduces the visibility of the laser marks on the glass surface, for example there is no light scattering due to the microcracks.

[0322] Figure 12 shows a schematic isometric view of a glass sheet 310 having two laser marks 317, 317’ on the major surface 312 of the glass sheet 310.

[0323] The first laser mark 317 is as shown in figures 3 and 4 and (with reference to figure 12) extends around the region 314. Also with reference to figure 11, the region 314 is that region that was programmed into the control system 304 and is a desired path for the deflected laser beam 303’ to follow. Suitably starting / stopping the laser allows only a portion of the perimeter of the region 314 to be laser marked according to the present invention.

[0324] The second laser mark 317’ extends around the region 314’ (which has the same dimensions as the region 314), but in contrast to the first laser mark 317, the protuberant portion extends around the entire perimeter of the region 314’. Again, this may be achieved by suitably starting / stopping the laser.

[0325] It is preferred that there is no overlap when the laser scans the region 314’ because any portion of the glass surface that is heated more than once by the laser beam may be subject to localised overheating and / or cracking, which is not desirable. Each laser mark 317, 317’ may be made using the same laser, one laser mark being made after the other. Alternatively, two lasers may be used, one for each laser mark and the laser marks may be made at the same time.

[0326] It is possible that the first laser mark 317 has a different height protuberant portion compared to the second laser mark 317’.

[0327] In order to determine the effect on glass strength of the laser marks on the glass surface, a number of sheets of clear soda-lime-silica float glass were marked with an array of laser marks of the type shown in figure 3 in order to carry out strength measurements. Each sample being tested was provided with an array of laser marks on the tin-side of each glass sheet, although similar tests may be carried out by laser marking the air-side of each glass sheet.

[0328] The sheets were 240mm x 240mm and 4mm thick and had been thermally strengthened to a degree by increasing the temperature of the glass sheet from room temperature to about 660°C, holding the heated glass sheet at that temperature for about 200 seconds, followed by cooling to ambient conditions which resulted in a surface compressive stress of about 10 - 20 MPa. Surface stress may be measured using a GASP photoelastic device such as a Strainoptics Laser GASP-CS. Such equipment is available from Strainoptics, Inc., 108 W. Montgomery Avenue, North Wales, PA 19454 USA. Fully annealed glass sheets may be used instead which will affect the baseline characteristic strength of the glass i.e. without any laser marks according to the invention thereon.

[0329] Each glass sheet for testing was heated and cooled as described above and provided on the tin-side with an array of laser marks arranged as illustrated in figure 13. In this example the laser marks on each glass sheet were made using a Keyence ML-Z9610 Laser Marker.

[0330] A scan speed of 300mm / s was used with a power density of about 0.15kW / mm2along a circular path of diameter 0.25mm to produce each laser mark in the array.

[0331] For the same settings except with a power density of about less than 0. 10-0.12kW / mm2, no laser mark could be observed in an NIC image of the type shown in figure 3.

[0332] For the same settings except with a power density of more than about 0. 15kW / mm2, micro-cracking was observed which is not desirable.

[0333] Samples were also prepared with the same settings except using power densities of about 0.19kW / mm2, 0.24kW / mm2, 0.29kW / mm2oand 0.39kW / mm2, but in these samples the laser marks became more visible to the unaided human eye probably due to the increased micro-cracking.

[0334] Back to figure 13, the array of laser marks consists of twenty-four rows of spaced apart laser marks, each row being parallel to an upper edge 402 of the glass sheet 400 being marked. For clarity, only the upper four rows are labelled (as I’, IF, III’ and IV’). Each row contains six spaced apart laser marks. In the row I’ only the laser mark la’ is labelled. In the row II’ only the laser marks Ila’ and lib ’ are labelled. In the row III’ only the laser mark Illa’ is labelled.

[0335] In each row adjacent laser marks are spaced apart by 40cm, and the laser marks at the end of each row are spaced apart from the lateral edges of the glass sheet 400 (by either 10cm or 30cm).

[0336] Adjacent rows are offset from each other by 10cm downwardly and 20cm horizontally such that the laser marks in the row directly beneath are offset from the laser marks immediately above.

[0337] The spacing between adjacent laser marks in each row was 20cm, and the laser marks in alternate rows are aligned vertically.

[0338] For example, the laser mark la’ is mid-way between the laser marks Ila’ and lib ’ and 10cm above the row II’. The laser mark Illa’ is mid-way between the laser marks Ila’ and lib’ and 10cm below the row the row II’. The laser mark Illa’ is directly below the laser mark la’ by 20cm.

[0339] In order to determine the characteristic strength of the laser marked glass sheets, twenty-five samples as described above were prepared and measured in accordance with ISO 1288-5 R60 using an Instron 5985 Materials Testing System. Each sample being tested was supported on a steel ring of radius 60mm and loaded via a loading ring of radius 20mm at a stressing rate of 2MPa / s, with the laser marked surface being in tension. Each sample was tested to failure.

[0340] It was found that the characteristic strength of the tin-side of 240mm x 240mm and 4mm thick soda-lime-silica float glass was about 147.5 MPa, whereas the laser marked samples described above (with the laser marks on the tin-side) had a characteristic strength of 103.5 MPa i.e. a reduction of about 30%.

[0341] Other arrays of laser marks may be used, for example where all the laser marks in each row are aligned with the laser marks in an adjacent row, or the laser marks in the array of laser marks may be random positioned.

[0342] Figures 14-17 illustrate some other shapes a laser mark in accordance with the present invention may have when viewed in plan, for example as shown in figures 3 and 4.

[0343] In Figure 14 the laser mark 500 has a protuberant portion 501 that extends around a circular region 503 (shown as a circular dotted line). The protuberant portion 501 has two ends 501a, 501b that face each other and may slightly touch or overlap, although this is not preferred as this may give rise to localised cracking as in the region of overlap when the protuberant portion is formed by a localised heat source such as a laser.

[0344] Figure 15 shows a laser mark 510 consisting of a first protuberant portion 511 and a second protuberant portion 512. The laser mark 510 extends around the rectangular region 513. The first and second protuberant portions 511, 512 have essentially the same “U” shape but arranged with the ends thereof facing each other.

[0345] The laser mark 510 extends around a rectangular region shown as dotted lined 513. The first protuberant portion 511 extends around an upper portion of the rectangular region 513 and the second protuberant portion 512 extends around a lower portion of the rectangular region 513.

[0346] Figure 16 shows a laser mark 520 consisting of two “C” shaped protuberant portions 521, 522 facing each other. The laser mark 520 extends around the region 523 which is substantially elliptical.

[0347] Figure 17 shows another laser mark 530 which has a protuberant portion 531 in the form of a spiral. An outer portion of the protuberant portion 531 lies on the perimeter of the region 533 and an inner portion of the protuberant portion 531 lies on the perimeter of the region 533’.

[0348] Figure 18 shows the view from inside a vehicle that has a windscreen 100 in accordance with the present invention.

[0349] The windscreen 100 is essentially the same as the laminated glazing 1 previously described. The vehicle windscreen has a lower peripheral edge extending between the points E and F. The vehicle windscreen has an upper peripheral edge extending between the points D and G.

[0350] On surface four (the inner facing surface) of the windscreen 100 are a plurality of laser marks, each laser mark including at least one respective protuberant portion, which may be straight or curved.

[0351] In this example each of the laser marks is of the type as shown in figure 3.

[0352] There is a first row I containing nine laser marks, only two of which are labelled li and Hi. The first row I is substantially parallel to the upper peripheral edge D-G of the windscreen 100. Beneath the first row I is a second row II also containing nine laser marks, only one of which is labelled IH. The second row II of laser marks is substantially parallel to the first row I of laser marks i.e. the laser marks in the row I lie along a first line and the laser marks in the row II lie along a second line, wherein the first line is parallel to the second line.

[0353] Beneath the second row II is a third row III containing eight laser marks. The second row II lies mid-way between the first row I and the third row III. The third row III is substantially parallel to the second row II.

[0354] Directly beneath the third row III is a fourth row IV also containing eight laser marks. Each corresponding laser mark in the row III and is aligned vertically with the corresponding laser mark in the row IV. Prior to forming the laser marks, the glass sheet is smooth. Following laser marking, the laser marks cause respective protuberant portions to be form at the glass surface. For example, each row contains a laser mark as shown in figure 3.

[0355] In order to test the effect of having portions of surface four of the laminated glazing laser marked, the ease with which a laminated glazing breaks following an impact on surface one may be used.

[0356] With reference to figure 19, a laminated glazing may be tested as follows.

[0357] A laminated glazing 151 to be tested is first positioned in a horizontally arranged frame (not shown) and clamped therein about the periphery. The major surface 159 (“surface one”) faces upwards and is able to be freely contacted i.e. the frame does not impede contact with the major surface 159.

[0358] An impactor 167 is dropped onto surface 159 at an impact location being a central position lying substantially on the centreline of the laminated 151 glazing, about 15cm - 30cm away from the lower peripheral edge of the laminated glazing, the actual distance away from the lower edge peripheral edge of the laminated glazing being kept the same in the tests.

[0359] The impactor 167 used in the tests may be a plastic hollow spheroid filled with steel shot and covered with felt. The overall weight of the impactor 167 may be 4.5kg and the overall diameter may be 165mm.

[0360] The impactor used in the tests is preferably similar to that specified in UN Regulation No. 127 (E / ECE / 324 / Rev.2 / Add. 126 / Rev.2).

[0361] The impactor 167 is positioned directly above the impact location at a height sufficient for the impactor to reach a speed of 40km / h at the impact location (by equating the potential energy to the acquired kinetic energy). The impactor 167 is directly above the impact location and will be released to fall under gravity in the direction of arrow 168 to strike the major surface 159 at the impact location. The impactor may be propelled towards the major surface 159 to achieve a certain velocity at impact.

[0362] To ensure the same impact position on each sample, a plumb line may be used to position the impactor 167 at the desired position for contact with the glass surface when dropped.

[0363] To assess the way the laminated glazing breaks when the impactor 167 is dropped onto the laminated glazing 151 as described above, the test may be recorded using a video camera 170 positioned above the laminated glazing 151. The video camera 170 operates at a high frame rate, for example a thousand frames per second (lOOOfps).

[0364] To classify the ease with which the laminated glazing 151 breaks, two breakage criteria can be identified by examining the video recording made during the test. A first breakage criteria referred to as an “Initial Breakage Time” may be obtained as the time taken for the first cracking to be seen in the laminated glazing following the impactor 167 making contact with the major surface 159 at the impact location.

[0365] A second breakage criteria referred to as a “Full Breakage Time” may be obtained as the time taken for the laminated glazing 151 to undergo catastrophic breakage following the impactor 167 making contact with the major surface 159 at the impact location.

[0366] To help identify the Initial Breakage Time and / or the Full Breakage Time, one or more reference marks may be provided on major surface 159, especially in the region of the chosen impact location. The reference marks may be in the form of a grid and may be applied to the major surface 159 using a suitable pen or the like.

[0367] It has been found that by having one or more laser marks having at least a first protuberant portion on a major surface of a laminated windscreen, the laminated glazing is easier to break in the event of a pedestrian colliding with the outer facing surface of the laminated windscreen. The protuberant portion may be sufficiently small and be raised relative to the adjacent glass surface such that the visibility thereof is sufficiently low to not be readily observable. This allows the laser marks to be provided in the through- vision region of a windscreen. Instead of using a laser, or as well as, other localised heat sources may be used to form the first protuberant portion.

Claims

CLAIMS1. A laminated glazing for a vehicle windscreen having a through-vision region and comprising a first sheet of glass joined to a second sheet of glass by an interlayer structure comprising at least one sheet of adhesive interlayer material, the first sheet of glass having a first major surface and an opposing second major surface; the second sheet of glass having a third major surface and an opposing fourth major surface; the laminated glazing being arranged such that the second major surface faces the third major surface; the laminated glazing having at least a first marked surface, the first marked surface being the first major surface, the second major surface, the third major surface or the fourth major surface, wherein the first marked surface has at least a first mark thereon; further wherein the first mark on the first marked surface comprises at least a first protuberant portion.

2. A laminated glazing according to claim 1, wherein the first protuberant portion is raised relative to an adjacent glass surface portion of the surface on which the first mark is on by at least lOnm, more preferably by at least 15nm, even more preferably at least 20nm and / or wherein the first protuberant portion is raised relative to an adjacent glass surface portion of the surface on which the first mark is on by 50pm or less.

3. A laminated glazing according to any of the preceding claims, wherein the first protuberant portion has a first edge and a second edge spaced apart therefrom defining a width of the first protuberant portion, and wherein the width of the first protuberant portion is less than 300pm, preferably less than 200pm and / or wherein the width of the first protuberant portion is at least 2pm.

4. A laminated glazing according to any of the preceding claims, wherein the first mark on the first marked surface has a maximum dimension of 20 mm or less and / or wherein the first mark on the first marked surface has a maximum dimension of 10 pm or more.

5. A laminated glazing according to any of the preceding claims, wherein the first and / or second sheet of glass has a surface compressive stress less than 100 MPa and / or a surface compressive stress of at least 5 MPa.

6. A laminated glazing according to any of the preceding claims, wherein the first mark on the first marked surface is spaced apart from at least a second mark on the first marked surface by a first space.

7. A laminated glazing according to claim 6, wherein the first space between the first mark and the second mark is at least 5mm and / or at most 500mm.

8. A laminated glazing according to any of the preceding claims, wherein the first mark extends around a first region of the first marked surface, the first region of the first marked surface having a perimeter and an area inboard of the perimeter, and wherein the first protuberant portion of the first mark lies on the perimeter of the first region of the first marked surface.

9. A laminated glazing according to claim 8, wherein the area of the first region is less than 50% of the area of the glass surface on which the first mark is on.

10. A laminated glazing according to claim 8 or claim 9, wherein the first region of the first marked surface has at least one curved side.

11. A laminated glazing according to any of the preceding claims, wherein the first protuberant portion has a length at least 30 pm and / or at most 10,000 pm.

12. A laminated glazing according to any of the preceding claims, wherein at least one of the first major surface, the second major surface, the third major surface and the fourth major surface has a coating on a least a portion thereof, preferably wherein the coating is adjacent the through vision region.

13. A laminated glazing according to claim 12, wherein the coating is on the first protuberant portion.

14. A laminated glazing according to claim 12, wherein the first mark is on the coating.

15. A laminated glazing according to any of the preceding claims, wherein the first mark is in the through-vision region.

16. A laminated glazing according to any of the preceding claims, wherein the first protuberant portion is produced by a localised heat source preferably comprising at least one of a laser, a plasma torch, a glass torch, a glass working lamp, a flame, and a heated fluid.

17. A method of making a laminated glazing comprising the steps (i) providing a first sheet of glass having a first major surface and a second opposing major surface; (ii) providing a second sheet of glass having a third major surface and a fourth major surface; (iii) directing a localised heat source onto the second sheet of glass to produce a first mark on the fourth major surface, the first mark having a first protuberant portion; and (iv) laminating the first sheet of glass to the second sheet of glass using an interlayer structure comprising at least a first adhesive interlayer.

18. A method according to claim 17, wherein the localised heat source comprises at least one of a laser, a plasma torch, a glass torch, a glass working lamp, a flame, and a heated fluid.

19. A method according to claim 17 or claim 18, wherein the first mark extends around a first region of the fourth major surface, the first region of the fourth major surface having a perimeter and an area inboard of the perimeter, the first protuberant portion of the first mark lying on the perimeter of the first region of the fourth major surface.

20. A method according to claim 19, wherein the first region of the fourth major surface is a predetermined first region on the fourth major surface, wherein step (iii) includes providing a control sequence to direct the localised heat source onto the second sheet of glass to follow a path defined by the predetermined first region on the fourth surface to produce the first mark on the fourth major surface.

21. A method according to any of the claims 17 to 20, wherein step (iii) takes place before step (iv).

22. A method according to claim 21, wherein following step (iv) the second major surface of the first sheet of glass faces the third major surface of the second sheet of glass; or wherein following step (iv) the fourth major surface of the second sheet of glass faces the first adhesive interlayer.

23. A method according to any of the claims 17 to 20, wherein step (iv) takes place before step (iii), preferably wherein the fourth major surface of the second sheet of glass is surface one or surface four of the laminated glazing.

24. A method according to any of the claims 17 to 20, further comprising a heating step before the marking step (iii), wherein the heating step comprises heating the first and / or second sheet of glass to a temperature suitable for shaping thereof, preferably between 580°C and 680°C.

25. A method according to claim 24, wherein the heating step comprises a shaping step after the first and / or second glass sheet has been heated to a temperature suitable for shaping.

26. A sheet of glass for a vehicle windscreen, the sheet of glass having a first major surface and a second opposing major surface, there being on the first major surface of the sheet of glass at least a first mark, and wherein the first mark comprises at least a first protuberant portion, preferably wherein the first protuberant portion is raised relative to an adjacent glass surface portion of the first major surface by at least lOnm.

27. A sheet of glass according to claim 26, having a surface compressive stress less than 100 MPa and / or at least 5 MPa.

28. A sheet of glass according to claim 26 or claim 27, wherein a coating is on the first protuberant portion.

29. A sheet of glass according to any of the claims 26 to 28, wherein the sheet of glass was made using a float process and has a tin-side and an air-side.

30. A sheet of glass according to claim 29, wherein the first mark is on the tin-side or the air-side.

31. A sheet of glass according to any of the claims 26 to 30, wherein the first major surface of the sheet of glass has a coating thereon, and the first mark is on the coating on the first major surface of the sheet of glass.

Images