Heating glazing with thinned outer sheet of glass and heating layer with flow separation lines

Abstract

A laminated glazing includes a first structural ply assembled with a first glass sheet of 0.5 to 1.5 mm thickness by way of a first adhesive interlayer, the first glass sheet forming a first exterior face of the laminated glazing, the face of the first glass sheet oriented toward the first adhesive interlayer bearing a first conductive heating layer of 2 ngstrms to 500 nm thickness, and the first conductive heating layer including flow-separating lines of 0.05 to 0.2 mm thickness spaced apart by 8 to 20 mm.

Claims

1. A laminated glazing comprising a first structural ply assembled with a first glass sheet of 0.5 to 1.5 mm thickness by way of a first adhesive interlayer, wherein said first glass sheet forms a first exterior face of the laminated glazing, intended to be in contact with exterior atmosphere and being chemically toughened, wherein a face of said first glass sheet oriented toward said first adhesive interlayer bears a first conductive heating layer of 2 ngstrms to 500 nm thickness, and wherein said first conductive heating layer comprises flow-separating lines of 0.05 to 0.2 mm thickness spaced apart by 8 to 20 mm, said lines being formed by etching in order to guide current between two current feed strips placed along two opposite edges of the glazing wherein the first structural ply is a sheet selected from the group consisting of a second glass sheet of thickness between 4 and 10 mm, a polymer sheet of thickness between 4 and 10 mm, and a polymer sheet of between 5 and 20 mm, and the first intermediate adhesive layer is a layer selected from the group consisting of a layer of polyvinyl butyral (PVB), polyurethane (PU), and poly(ethylene vinyl acetate) (EVA) having a thickness between 0.5 and 20 mm, and a second structural ply assembled with the first structural ply by way of a second adhesive interlayer; and a second glass sheet of 0.5 to 1.5 mm thickness assembled with said first structural ply or said second structural ply by way of a third adhesive interlayer.

2. The laminated glazing as claimed in claim 1, wherein said second glass sheet forms a second exterior face of the laminated glazing, and wherein a face of said second glass sheet oriented toward said third adhesive interlayer bears a second conductive heating layer of 2 ngstrms to 500 nm thickness.

3. The laminated glazing as claimed in claim 2, wherein said second conductive heating layer comprises flow-separating lines of 0.05 to 0.2 mm thickness, said lines being spaced apart by 8 to 20 mm.

4. The laminated glazing as claimed in claim 2, wherein said first conductive heating layer and said second conductive heating layer consist, independently of each other, of a layer of a conductive oxide of 20 to 500 nm thickness, or of a layer of a metal of 2 to 100 ngstrms thickness.

5. The laminated glazing as claimed in claim 4, wherein said conductive oxide is tin-doped indium oxide (ITO), fluorine-doped tin oxide (SnO.sub.2:F) or aluminum-doped zinc oxide (AZO), and said metal is gold.

6. The laminated glazing as claimed in claim 3, wherein the flow-separating lines are arranged in substantially parallel lines that connect substantially orthogonally to two current feed strips and that have curvatures or inflections when said two facing strips or portions of said two strips make an angle to each other or one another.

7. The laminated glazing as claimed in claim 2, wherein said first conductive heating layer or said second conductive heating layer has a thickness gradient.

8. The laminated glazing as claimed in claim 1, wherein said first structural ply and said second structural ply each consist, independently of each other, of a glass sheet of thickness comprised between 4 and 10 mm or of a polymer of thickness comprised between 5 and 20 mm.

9. The laminated glazing as claimed in claim 8, wherein said first structural ply and said second structural ply each consist, independently of each other, of a chemically toughened or semi-thermally-tempered glass sheet, or of polymethyl methacrylate (PMMA) or of polycarbonate (PC).

10. The laminated glazing as claimed in claim 1, wherein said second glass sheet of 0.5 to 1.5 mm thickness is chemically toughened.

11. The laminated glazing as claimed in claim 1, wherein said first adhesive interlayer, said second adhesive interlayer and said third adhesive interlayer consist, independently of one another, of a layer of polyvinyl butyral (PVB), polyurethane (PU) or ethylene vinyl acetate (EVA) of 0.5 to 20 mm thickness.

12. The laminated glazing as claimed in claim 11, wherein said first adhesive interlayer, said second adhesive interlayer and said third adhesive interlayer consist, independently of one another, of a layer of polyvinyl butyral (PVB), polyurethane (PU) or ethylene vinyl acetate (EVA) of 1 to 16 mm thickness.

13. A method comprising utilizing a laminated glazing as claimed in claim 1 as a helicopter or airplane cockpit glazing.

14. The method as claimed in claim 13, wherein the laminated glazing is utilized as an anti-frost glazing.

15. The method as claimed in claim 13, wherein the laminated glazing is utilized as an antifog glazing.

16. The laminated glazing as claimed in claim 1, wherein the first conductive heating layer consists of a metal of 2 to 100 ngstrms thickness.

Description

(1) The invention will be better understood in light of the description of the appended drawings, in which:

(2) FIG. 1 shows curves of optimal setpoint temperature as a function of the ratio of the heating power at the cold point to the heating power at the point of regulation, this ratio being designated K.sub.c, for various thicknesses of the glass sheet making contact with the exterior atmosphere of the laminated glazing;

(3) FIGS. 2a, 2b, and 2c are schematic representations of a known heated laminated glazing and two embodiments of a glazing unit according to the invention.

(4) FIGS. 3a and 3b are curves of heating power and of the decrease in heating power, respectively, for various configurations of the laminated glazing.

(5) FIG. 4 is a top plan view of a glazing in accordance with an embodiment.

(6) With reference to FIG. 1, it may be seen that, for each of the thicknesses of the exterior glass sheet, the more uniform the temperature of the heated glazing is over its entire area, i.e. the closer the ratio of the heating powers at the cold point/sensor is to 1, the lower the optimal setpoint temperature (measured at the sensor).

(7) Essentially, the thinner the exterior glass sheet, the lower the optimal setpoint temperature. For a ratio K.sub.c of powers at the cold point/sensor of 0.7, the optimal setpoint temperature decreases from 31 C. for an exterior glass sheet of 3 mm thickness to an optimal setpoint temperature of 17 C. for an exterior glass sheet of 0.8 mm thickness.

(8) The curves in FIG. 1 were obtained from calculations that were based on assumptions vis--vis convection and the collection of water on the glazing, assumptions that of course were the same for all three curves in the figure.

(9) FIGS. 2a and 2b show two aircraft-windshield glazing configurations in cross section, the configuration in FIG. 2a being a conventional configuration and the configuration in FIG. 2b being a thin-glass configuration.

(10) Each of the two laminated glazings 1 comprises first and second structural plies 4, 6, each formed from a fully thermally tempered (compressive surface stress of about 150 MPa) or chemically toughened soda-lime-silica glass sheet of 8 mm thickness. The glass is not necessarily soda-lime-silica glass, and may be aluminosilicate or lithium aluminosilicate glass, etc. The plies 4, 6 are adhesively bonded by a layer 5 of polyvinyl butyral of 2 mm thickness. The ply 6 forms the exterior face 22 of the laminated glazing 1, on the cabin-interior side.

(11) A semi-thermally tempered or chemically toughened glass sheet 2 of 3 mm thickness (case of FIG. 2a), or a chemically toughened glass sheet of 0.8 mm thickness (case of FIG. 2b), is adhesively bonded to the first structural ply 4 by way of a polyvinyl butyral layer 3 of 8 mm thickness. The glass sheet 2 forms the exterior face 21 of the laminated glazing 1, on the cabin-exterior side. The face of the glass sheet 2 oriented toward the interior of the laminate bears a conductive heating layer 11 of tin-doped indium oxide (ITO) of 200 nm thickness, optionally comprising, depending on the sample, flow-separating lines of 0.08 mm thickness spaced apart by 10 mm, said lines being formed by laser etching.

(12) In an embodiment, the laminated glazing includes a second glass sheet forming the second exterior face 22 of the laminated glazing and having a second conductive heating layer 23 assembled with the first structural ply 4 or the second structural ply 6 by way of a third adhesive interlayer 25. The second conductive heating layer 23 is on a side of the second glass sheet oriented towards the third adhesive interlayer 25.

(13) The presence or absence of flow-separating lines 26 or flow lines allows different heating power uniformities to be obtained, these uniformities being characterized by the ration of the power delivered by the current feed strips 28 to the coldest zone of the glazing to the power delivered level with the regulating probe: 0.6 without flow lines and 0.8 with flow lines, in the present case.

(14) The electrical power consumption of the glazing as a function of ambient temperature was then calculated under the convective conditions of flight under dry conditions (150 W/m.sup.2/ C.). It is assumed here that the probe is representative of the average power of the glazing.

(15) For these calculations, the setpoint temperature was adapted to the glazing.

(16) The results are given in the form of curves in FIGS. 3a and 3b, which are equivalent and which show that, with respect to the glazing with the relatively thick glass of FIG. 2a without flow lines, the decrease in the average delivered power (in W/m.sup.2) increases for the respective solutions in which: the glass is 0.8 mm thick (FIG. 2b) and flow lines are absent; the glass is 3 mm thick (FIG. 2a) and flow lines are present; the glass is 0.8 mm thick and flow lines are present.

(17) The improvement is particularly great for helicopters, which frequently encounter flight conditions between 10 C. and 30 C.

(18) The constant portion of the two assembly configurations shown in FIGS. 2a and 2b may be replaced by one ply or two plies of PMMA or PC of total thickness typically of 5 to 30 mm. These small thicknesses rather correspond to helicopter applications. Two structural plies made of polymer may be adhesively bonded to each other by a layer of polyurethane.